Telegram SMS Verification Code Not Received When Changing Number

I am a Telegram user and I am trying to change my registered phone number from a US number to a Nigerian number. However, when I attempt to do this, I do not receive the SMS verification code that is required to complete the number change. Today I tried several times to receive the code on my Nigerian line but it never arrived. Instead, I see a screen about SMS fees and an offer for a one‑week Telegram Premium subscription in Nigerian naira, but I am not able to proceed with a normal free SMS verification to change my number. I would like Telegram to help me change my phone number from my US number to my Nigerian number without extra charges and to ensure that the SMS verification works properly, or to provide me with an alternative free verification method so that I can keep using my account safely.