View Source ExTDLib.Method.ChangePhoneNumber (ExTDLib v0.0.4)

Changes the phone number of the user and sends an authentication code to the user's new phone number; for official Android and iOS applications only. On success, returns information about the sent code. Returns object_ptr<AuthenticationCodeInfo>.

NameTypeDescription
phone_numberstringThe new phone number of the user in international format.
settingsphoneNumberAuthenticationSettingsSettings for the authentication of the user's phone number; pass null to use default settings.

More details on telegram's documentation.