Contact your carrier to change your phone number
Ask the carrier to assign a new number to your SIM or eSIM
Go to Settings
Tap Cellular or Mobile Data
Select your cellular plan
Tap Remove Cellular Plan if needed
Add the new plan or activate the updated number from your carrier
Restart your iPhone
Open Settings
Tap Messages
Turn iMessage off and back on
Open Settings
Tap FaceTime
Turn FaceTime off and back on
Update your number in apps and accounts that use your phone number
Notify your contacts of your new number