Hi Will
Phoneboxes have a descriptive location, to be used when making emergency calls. That could be mapped, I am not sure if there is a tag for it but it is certainly not the name tag. We certainly map the phonenumber.

I noticed that you have add disused:amenity to this object, yet amenity=phonebox is stll there.
If it is no longer used it should be disused:amenity=phonebox. As it stands it still renders and will appear in searches, which can be misleading to map users.

Cheers Phil