I cant deregister my phone number because its more than 10 digits.
Im currently on holiday in my home country for a few months. While here Id like to keep my iMessage number the same instead of switching to my local number. Im trying to deregister my local phone number via the website https://selfsolve.apple.com/deregister-imessage/ however I cant input my full phone number as its more than 10 digits. Ive tried to read another forum post about it but it wasn't helpful. (Yes, Ive already changed the country code).
iPhone 13, iOS 15