Changed phone and changed phone number
I can’t change phone numbers because it won’t let me
I can’t change phone numbers because it won’t let me
You can't change numbers by yourself.
Contact your carrier for help.
If you mean the number in the phone is not the one in the SIM then…
Settings, Apps, Messages, turn off iMessage
Settings, Apps, Facetime, turn off Facetime
restart the phone
Settings, Apps, Messages, turn on iMessage
Settings, Apps, Facetime, turn on Facetime
Did you contact your carrier for help with this?
Changed phone and changed phone number