New mobile number for Verification Process

Hi there I no longer have the phone number registered on my PTA...how do I change it to my current one, so that I can complete the verification process. I seem to be going round in circles. When I called the helpline yesterday she td me to click on the link to change my mobile number...but I can't find it. Can anyone help please?

Hi,

If you are unable to find the option, you will need to contact our online services team to go through the process with you:

Technical support with HMRC online services

Thank you.