If You Have Another Active Telegram Session:
Log in on the new device using your old phone number. The verification code will be sent to your active Telegram session on your other logged-in device.
Once logged in, immediately change your phone number (Settings > Tap on your phone number > Change Number) to your new, accessible number.
If You Have NO Active Sessions & NO Access to Old Number:
Regain Old Number: Your best bet is to try to regain telegram number database access to your old phone number from your mobile carrier (e.g., get a new SIM with the old number).
Telegram Support (Low Success): You can try contacting Telegram Support via telegram.org/support, but without access to the number or an active session, proving ownership is very difficult.
Prevention is Key: This scenario highlights the critical importance of 2FA with a recovery email and keeping at least one active Telegram session.
VII. Bypassing Personal Numbers: Anonymous Options
For ultimate privacy or team accounts.
Anonymous Numbers via Fragment (+888 Numbers):
Telegram's official blockchain-based numbers (purchased with Toncoin on fragment.com/numbers).
They are not tied to traditional SIM cards or personal identity. Verification codes go to your TON wallet/Fragment.
Ideal for creating truly anonymous Telegram accounts.
Acquire a number from a VoIP service (paid services like Hushed, Burner are more reliable than free ones).
Use this number for Telegram registration. Verification codes are received via the VoIP app/dashboard.
Good for separating your personal number from your Telegram identity.