unlimited broadband

[john6767]

23 minutes ago, Tony Brooks said:

having changed two sim cards recently because of needing a smaller one I know the sim has a number (not the phone number on it) and the provider use that to link to the actual phone number within their computer systems. When you change provider they link your old number to the new sim inside their computers.

Yep that is what I would say happens, the point being the phone does not come into it at all.