Temporary number appears on setting/phone/my phone even after porting of the old number is successful

Hi the temporary number still appears on my setting/phone/my phone even after the my old number has been ported over. I tried changing it to the old number but it wouldn’t let me save the old number . It is a problem as the Apple ID is registered to my old number . I have tried taking the SIM out then restarting again but it doesn’t help.