iPhone AutoFill in Safari

I have my AutoFill all set-up using my contact info and it's turned on in Safari on my iPhone X.

It all works fine when i'm filling in a form on safari apart from 'mobile number'. I've got my mobile number set-up correct in the right format of country code and number and i've tried turning off autofill and force re-starting my iPhone and it's still not working. I don't actually remember my mobile number ever working on autofill.

I'm on iOS 14.4.2 (latest version at the time of raising this issue).

Can anyone help??

It's such a small frustrating thing as I fill in forms and buy online all the time and it really niggles at me that my mobile number won't auto populate like the rest of my details (name, address etc).

Can anyone help fix this issue or has experienced the same thing and knows a way to resolve it?

Thanks