diff --git a/docs/SUMMARY.md b/docs/SUMMARY.md
index 637633c..f9e4d5e 100644
--- a/docs/SUMMARY.md
+++ b/docs/SUMMARY.md
@@ -20,7 +20,7 @@
     - [Search Gifts](client/marketplace/search-gifts.md)
   - Ads
     - [Overview](client/ads/overview.md)
-    - [Top Up TON](client/ads/topup-ton.md)
+    - [Top Up GRAM](client/ads/topup-gram.md)
     - [Recharge Ads](client/ads/recharge-ads.md)
   - Anonymous Numbers
     - [Overview](client/anonymous-numbers/overview.md)
diff --git a/docs/advanced/troubleshooting.md b/docs/advanced/troubleshooting.md
index 4878d77..1eed9fb 100644
--- a/docs/advanced/troubleshooting.md
+++ b/docs/advanced/troubleshooting.md
@@ -43,7 +43,7 @@ Symptoms:
 
 Actions:
 
-- keep TON reserve for fees,
+- keep GRAM (ex TON) reserve for fees,
 - ensure USDT is on the **Fragment-linked wallet**,
 - retry after short delay when seqno collisions happen.
 - check operation constraints in Stars/Premium/Ads method pages.
diff --git a/docs/client/ads/overview.md b/docs/client/ads/overview.md
index a6659da..118a4ec 100644
--- a/docs/client/ads/overview.md
+++ b/docs/client/ads/overview.md
@@ -2,10 +2,10 @@
 
 Ads flow is split into two methods:
 
-- [Top Up TON](topup-ton.md)
+- [Top Up GRAM](topup-gram.md)
 - [Recharge Ads](recharge-ads.md)
 
-Use the first method to send TON to a Telegram user.
+Use the first method to send GRAM (ex TON) to a Telegram user.
 Use the second method to fund your own Telegram Ads account.
 
 ## Common errors
diff --git a/docs/client/ads/topup-gram.md b/docs/client/ads/topup-gram.md
new file mode 100644
index 0000000..ff4ce96
--- /dev/null
+++ b/docs/client/ads/topup-gram.md
@@ -0,0 +1,38 @@
+# Top Up GRAM
+
+Use this method to send GRAM (ex TON) to a user's Telegram balance.
+
+## Method
+
+```python
+await client.topup_gram(
+    username: str,
+    amount: int,
+    show_sender: bool = True,
+) -> AdsTopupResult
+```
+
+## Parameters
+
+- `username`: recipient Telegram username — `@username`, `username`, or `https://t.me/username`
+- `amount`: integer from `1` to `1_000_000_000`
+- `show_sender`: controls sender visibility
+
+**`amount` must be an integer in the allowed range.**
+
+## Return
+
+- `AdsTopupResult(transaction_id, username, amount)`
+
+## Typical errors
+
+- `ConfigurationError`: invalid amount
+- `UserNotFoundError`: recipient not found on Fragment
+- `WalletError`: insufficient GRAM (ex TON) balance
+
+## Example
+
+```python
+result: AdsTopupResult = await client.topup_gram("@username", amount=10, show_sender=True)
+print(result.transaction_id)
+```
diff --git a/docs/client/ads/topup-ton.md b/docs/client/ads/topup-ton.md
deleted file mode 100644
index 657152f..0000000
--- a/docs/client/ads/topup-ton.md
+++ /dev/null
@@ -1,32 +0,0 @@
-# Top Up TON
-
-Use this method to send TON to a user's Telegram balance.
-
-## Method
-
-```python
-await client.topup_ton(
-    username: str,
-    amount: int,
-    show_sender: bool = True,
-) -> AdsTopupResult
-```
-
-## Parameters
-
-- `username`: recipient Telegram username
-- `amount`: integer from `1` to `1_000_000_000`
-- `show_sender`: controls sender visibility
-
-**Important:** `amount` must be an integer in the allowed range.
-
-## Return
-
-- `AdsTopupResult(transaction_id, username, amount)`
-
-## Example
-
-```python
-result: AdsTopupResult = await client.topup_ton("@username", amount=10, show_sender=True)
-print(result.transaction_id)
-```
diff --git a/docs/client/overview.md b/docs/client/overview.md
index 9fbeac2..56143c2 100644
--- a/docs/client/overview.md
+++ b/docs/client/overview.md
@@ -19,7 +19,7 @@ Main async methods on `FragmentClient`:
 - `purchase_premium(...)`
 - `giveaway_stars(...)`
 - `giveaway_premium(...)`
-- `topup_ton(...)`
+- `topup_gram(...)`
 - `recharge_ads(...)`
 - `get_wallet()`
 - `get_login_code(...)`
diff --git a/docs/client/premium/giveaway.md b/docs/client/premium/giveaway.md
index 3c88c05..1f9c246 100644
--- a/docs/client/premium/giveaway.md
+++ b/docs/client/premium/giveaway.md
@@ -9,7 +9,7 @@ await client.giveaway_premium(
     channel: str,
     winners: int,
     months: int = 3,
-    payment_method: PaymentMethod = "ton",
+    payment_method: PaymentMethod = PaymentMethod.GRAM,
 ) -> PremiumGiveawayResult
 ```
 
@@ -18,7 +18,7 @@ await client.giveaway_premium(
 - `channel`: accepts `@channel`, `channel`, or `https://t.me/channel`
 - `winners`: integer from `1` to `24_000`
 - `months`: one of `3`, `6`, `12`
-- `payment_method`: `"ton"` or `"usdt_ton"`
+- `payment_method`: `PaymentMethod.GRAM` (default), `PaymentMethod.USDT_GRAM`, or any other `PaymentMethod` value
 
 **`winners` must be a positive integer, and large values can increase total cost significantly.**
 
diff --git a/docs/client/premium/purchase.md b/docs/client/premium/purchase.md
index 2fdcdbd..72cee14 100644
--- a/docs/client/premium/purchase.md
+++ b/docs/client/premium/purchase.md
@@ -9,7 +9,7 @@ await client.purchase_premium(
     username: str,
     months: int,
     show_sender: bool = True,
-    payment_method: PaymentMethod = "ton",
+    payment_method: PaymentMethod = PaymentMethod.GRAM,
 ) -> PremiumResult
 ```
 
@@ -18,7 +18,7 @@ await client.purchase_premium(
 - `username`: accepts `@username`, `username`, or `https://t.me/username`
 - `months`: one of `3`, `6`, `12`
 - `show_sender`: controls sender visibility on recipient side
-- `payment_method`: `"ton"` or `"usdt_ton"`
+- `payment_method`: `PaymentMethod.GRAM` (default), `PaymentMethod.USDT_GRAM`, or any other `PaymentMethod` value
 
 **`months` only supports `3`, `6`, or `12`.**
 
@@ -36,6 +36,6 @@ await client.purchase_premium(
 ## Example
 
 ```python
-result: PremiumResult = await client.purchase_premium("@username", months=6, payment_method="ton")
+result: PremiumResult = await client.purchase_premium("@username", months=6, payment_method=PaymentMethod.GRAM)
 print(result.transaction_id)
 ```
diff --git a/docs/client/stars/giveaway.md b/docs/client/stars/giveaway.md
index 5d783c0..fc2e3c1 100644
--- a/docs/client/stars/giveaway.md
+++ b/docs/client/stars/giveaway.md
@@ -9,16 +9,16 @@ await client.giveaway_stars(
     channel: str,
     winners: int,
     amount: int,
-    payment_method: PaymentMethod = "ton",
+    payment_method: PaymentMethod = PaymentMethod.GRAM,
 ) -> StarsGiveawayResult
 ```
 
 ## Parameters
 
 - `channel`: accepts `@channel`, `channel`, or `https://t.me/channel`
-- `winners`: integer from `1` to `5`
+- `winners`: integer from `1` to `15`
 - `amount`: integer from `500` to `1_000_000` (per winner)
-- `payment_method`: `"ton"` or `"usdt_ton"`
+- `payment_method`: `PaymentMethod.GRAM` (default), `PaymentMethod.USDT_GRAM`, or any other `PaymentMethod` value
 
 **Each winner receives the full `amount` value.**
 
diff --git a/docs/client/stars/purchase.md b/docs/client/stars/purchase.md
index 7a55435..34494e6 100644
--- a/docs/client/stars/purchase.md
+++ b/docs/client/stars/purchase.md
@@ -9,18 +9,18 @@ await client.purchase_stars(
     username: str,
     amount: int,
     show_sender: bool = True,
-    payment_method: PaymentMethod = "ton",
+    payment_method: PaymentMethod = PaymentMethod.GRAM,
 ) -> StarsResult
 ```
 
 ## Parameters
 
 - `username`: accepts `@username`, `username`, or `https://t.me/username`
-- `amount`: integer from `50` to `1_000_000`
+- `amount`: integer from `50` to `10_000_000`
 - `show_sender`: controls sender visibility on recipient side
-- `payment_method`: `"ton"` or `"usdt_ton"`
+- `payment_method`: `PaymentMethod.GRAM` (default), `PaymentMethod.USDT_GRAM`, or any other `PaymentMethod` value
 
-**Amount must be between `50` and `1_000_000`.**
+**Amount must be between `50` and `10_000_000`.**
 
 ## Return
 
@@ -36,6 +36,6 @@ await client.purchase_stars(
 ## Example
 
 ```python
-result: StarsResult = await client.purchase_stars("@username", amount=500, payment_method="ton")
+result: StarsResult = await client.purchase_stars("@username", amount=500, payment_method=PaymentMethod.GRAM)
 print(result.amount)
 ```
diff --git a/docs/getting-started/configuration.md b/docs/getting-started/configuration.md
index 933cc08..2282f36 100644
--- a/docs/getting-started/configuration.md
+++ b/docs/getting-started/configuration.md
@@ -8,19 +8,21 @@ FragmentClient(
     api_key: str,
     cookies: dict[str, Any] | str,
     wallet_version: str = "V5R1",
+    api_provider: str = "tonapi",
     timeout: float = 30.0,
 )
 ```
 
 ## Parameters
 
-- `seed`: wallet mnemonic (**12, 18, or 24 words**)
-- `api_key`: Tonapi key from https://tonconsole.com
+- `seed`: wallet mnemonic (**12 or 24 words**)
+- `api_key`: API key — from [tonconsole.com](https://tonconsole.com) (tonapi) or [@toncenter](https://t.me/toncenter)
 - `cookies`: Fragment cookies as a dictionary or JSON string
-- `wallet_version`: `"V4R2"` or `"V5R1"`
+- `wallet_version`: `"V4R2"`, `"V5R1"`, `"HighloadV2"`, or `"HighloadV3R1"`
+- `api_provider`: blockchain API provider — `"tonapi"` (default) or `"toncenter"`
 - `timeout`: request timeout in seconds
 
-**If `api_key` is too short or cookies are incomplete, initialization fails immediately.**
+**If `api_key` or cookies are missing, initialization fails immediately.**
 
 ## Required cookies
 
@@ -34,26 +36,34 @@ FragmentClient(
 ```python
 from pyfragment import FragmentClient
 
-client = FragmentClient(
+async with FragmentClient(
     seed="word1 word2 ... word24",
-    api_key="YOUR_TONAPI_KEY",
+    api_key="YOUR_API_KEY",
     cookies={
         "stel_ssid": "...",
         "stel_dt": "...",
         "stel_token": "...",
         "stel_ton_token": "...",
     },
-)
-```
-
-Use it inside async context manager:
-
-```python
-async with client:
+) as client:
     wallet = await client.get_wallet()
 ```
 
-You can also create the client directly inside `async with` if you prefer one-block setup.
+## Switching API provider
+
+By default, the library uses [tonconsole.com](https://tonconsole.com) (tonapi). To use [toncenter](https://t.me/toncenter) instead, pass `api_provider="toncenter"`:
+
+```python
+async with FragmentClient(
+    seed="...",
+    api_key="YOUR_TONCENTER_API_KEY",
+    cookies={...},
+    api_provider="toncenter",
+) as client:
+    ...
+```
+
+Both providers work identically — the correct `tonutils` client is selected automatically based on `api_provider`.
 
 ## Validation behavior
 
@@ -62,8 +72,7 @@ At initialization, library validates:
 - seed format,
 - cookie shape and required keys,
 - supported wallet version,
+- supported API provider,
 - parseability of cookie JSON strings.
 
 Constructor-level issues are raised as `ConfigurationError` or `CookieError`.
-
-**Tip:** keep validation failures visible in logs during initial integration. They save a lot of debugging time.
diff --git a/docs/getting-started/credentials-and-cookies.md b/docs/getting-started/credentials-and-cookies.md
index 97abbc1..13c742d 100644
--- a/docs/getting-started/credentials-and-cookies.md
+++ b/docs/getting-started/credentials-and-cookies.md
@@ -8,7 +8,7 @@ Generate an API key at https://tonconsole.com.
 
 ## Seed phrase
 
-Use your TON wallet mnemonic.
+Use your GRAM (ex TON) wallet mnemonic.
 
 - **Keep it private.**
 - **Never log it or commit it to git.**
diff --git a/docs/getting-started/quickstart.md b/docs/getting-started/quickstart.md
index fa8d816..139b895 100644
--- a/docs/getting-started/quickstart.md
+++ b/docs/getting-started/quickstart.md
@@ -6,21 +6,33 @@ Use this minimal example to verify that your credentials, cookies, and wallet se
 import asyncio
 
 from pyfragment import FragmentClient
+from pyfragment.enums import PaymentMethod
 
 
 async def main() -> None:
     async with FragmentClient(
         seed="word1 word2 ... word24",
-        api_key="YOUR_TONAPI_KEY",
+        api_key="YOUR_API_KEY",  # tonconsole.com (tonapi, default) or t.me/toncenter
         cookies={
             "stel_ssid": "...",
             "stel_dt": "...",
             "stel_token": "...",
             "stel_ton_token": "...",
         },
+        wallet_version="V5R1",   # or "V4R2", "HighloadV2", "HighloadV3R1"
+        api_provider="tonapi",   # or "toncenter"
     ) as client:
         wallet = await client.get_wallet()
-        print(wallet)
+        print(f"GRAM: {wallet.gram_balance} | USDT: {wallet.usdt_balance}")
+
+        recipient = "https://t.me/username"  # also: @username, username
+
+        stars = await client.purchase_stars(recipient, amount=500, payment_method=PaymentMethod.USDT_GRAM)
+        print(f"Sent {stars.amount} Stars to {stars.username} | tx: {stars.transaction_id}")
+
+        premium = await client.purchase_premium(recipient, months=6, payment_method=PaymentMethod.GRAM)
+        print(f"Sent Premium {premium.amount}m to {premium.username} | tx: {premium.transaction_id}")
+
 
 asyncio.run(main())
 ```
diff --git a/docs/reference/errors.md b/docs/reference/errors.md
index 80a7e2d..c7fe129 100644
--- a/docs/reference/errors.md
+++ b/docs/reference/errors.md
@@ -11,6 +11,7 @@ Good error handling is the difference between a stable integration and random pr
   - `FragmentAPIError`
     - `FragmentPageError`
     - `UserNotFoundError`
+    - `AlreadySubscribedError`
     - `AnonymousNumberError`
     - `TransactionError`
     - `ParseError`
@@ -44,7 +45,9 @@ except FragmentError:
 
 ## Method-to-error mapping
 
-- Stars/Premium purchase and giveaway: `ConfigurationError`, `UserNotFoundError`, `WalletError`, `VerificationError`
+- Stars purchase: `ConfigurationError`, `UserNotFoundError`, `WalletError`, `VerificationError`
+- Premium purchase: `ConfigurationError`, `UserNotFoundError`, `AlreadySubscribedError`, `WalletError`, `VerificationError`
+- Stars/Premium giveaway: `ConfigurationError`, `UserNotFoundError`, `WalletError`, `VerificationError`
 - Ads operations: `ConfigurationError`, `UserNotFoundError`, `WalletError`, `VerificationError`
 - Cookies/auth setup: `CookieError`, `ConfigurationError`, `FragmentPageError`
 
diff --git a/docs/reference/literals.md b/docs/reference/literals.md
index 01eee5e..48dfcd2 100644
--- a/docs/reference/literals.md
+++ b/docs/reference/literals.md
@@ -2,22 +2,52 @@
 
 These literals describe accepted string values for key method parameters.
 
+## ApiProvider
+
+```python
+from pyfragment.enums import ApiProvider
+
+ApiProvider.TONAPI    # tonconsole.com — default
+ApiProvider.TONCENTER # t.me/toncenter
+```
+
+Pass as string to `FragmentClient(api_provider=...)`:
+
+```python
+FragmentClient(..., api_provider="tonapi")    # default
+FragmentClient(..., api_provider="toncenter")
+```
+
 ## PaymentMethod
 
 ```python
-PaymentMethod = Literal["ton", "usdt_ton"]
+from pyfragment.enums import PaymentMethod
+
+PaymentMethod.GRAM        # GRAM (ex TON) — default
+PaymentMethod.USDT_GRAM   # USDT on GRAM (ex TON)
+PaymentMethod.USDT_ETH    # USDT on Ethereum
+PaymentMethod.USDT_POL    # USDT on Polygon
+PaymentMethod.USDC_ETH    # USDC on Ethereum
+PaymentMethod.USDC_BASE   # USDC on Base
+PaymentMethod.USDC_POL    # USDC on Polygon
 ```
 
 ## WalletVersion
 
 ```python
-WalletVersion = Literal["V4R2", "V5R1"]
+from pyfragment.enums import WalletVersion
+
+WalletVersion.V5R1       # default
+WalletVersion.V4R2
+WalletVersion.HighloadV2
+WalletVersion.HighloadV3R1
 ```
 
-These literals are exported from `pyfragment` (top-level), `pyfragment.models`, and `pyfragment.models.enums`.
+All enums are exported from both `pyfragment` (top-level) and `pyfragment.enums`.
 
 ## Usage notes
 
+- Use `ApiProvider` when configuring the blockchain API provider in `FragmentClient`.
 - Use `PaymentMethod` for purchase and giveaway operations.
 - Use `WalletVersion` when configuring `FragmentClient`.
 
diff --git a/docs/reference/models.md b/docs/reference/models.md
index 622b0d4..3d7c740 100644
--- a/docs/reference/models.md
+++ b/docs/reference/models.md
@@ -11,7 +11,7 @@ Exported result models:
 - `AdsRechargeResult(transaction_id, amount)`
 - `StarsGiveawayResult(transaction_id, channel, winners, amount)`
 - `PremiumGiveawayResult(transaction_id, channel, winners, amount)`
-- `WalletInfo(address, state, ton_balance, usdt_balance)`
+- `WalletInfo(address, state, gram_balance, usdt_balance)`
 - `LoginCodeResult(number, code, active_sessions)`
 - `TerminateSessionsResult(number, message)`
 - `UsernamesResult(items, next_offset_id)`
@@ -26,7 +26,7 @@ Most high-level methods return one of these dataclasses.
 - `purchase_premium()`: `PremiumResult`
 - `giveaway_stars()`: `StarsGiveawayResult`
 - `giveaway_premium()`: `PremiumGiveawayResult`
-- `topup_ton()`: `AdsTopupResult`
+- `topup_gram()`: `AdsTopupResult`
 - `recharge_ads()`: `AdsRechargeResult`
 - `get_wallet()`: `WalletInfo`
 - `get_login_code()`: `LoginCodeResult`