Mobile CRM customising contact data fields

Hi

I'm a bit stuck, been attempting to remove some fields displayed in mobile CRM so they match our desktop version, I want to create consistency across devices.

To remove fields I followed what I believe to be the right path. for example Admin/customisation/person/screens. I then switched under Devices to mobile devices (iphone).

Yet the fields I'm trying to remove aren't listed when I click through relevant screen caption. The first two I'd like to remove are Country code and Area code at company and person level

Does anyone know a fix for this please?

Thanks

Claire