Thanks for posting in regards to changing your mobile number, we appreciate you taking the time to raise this via the forums and welcome to the community.
Is there a specific reason you're looking to change the number? Are you looking to bring an existing number over to a new account from another provider? Or just looking to change for another reason?
If it is a change of number for one from a previous advisor we would need a PAC code from the original provider. Let me know here and I'm happy to help.