Need help with Mobile Phone update in account

[David Ian Fayloga Viloria]

I created a new account due to old account was placed in archives for no activity for more than 4 years. I tried entering my mobile phone to my new account, but the system still recognized that the phone number is still being used. Instead, I used another phone number just to fully activate my account which is not my mobile phone.

How do I go about updating my account with my mobile phone number?

I would really appreciate any help or inputs.