Are all numbers with a prefixed code begining with 07 for mobile phones only. I was surprised to find that the customer service centre for T Mobile has a number begining with 07 when you call them from a landline. Surely the call centre employees aren't all sitting with mobiles stuck to their ears! but the charge for the call is as if that is indeed the case.
T-mobile's customer service number is a local call 0845 number from within the UK. Only when calling from abroad is it an "07" number and you pay international call charges. I do believe that all mobiles in UK have numbers starting with "07" and it's been that way for a few years now. Whether or not that means that all "07" numbers must be mobiles I don't really know.
07 numbers are always connected via the mobile network (and hence incur mobile charges) but the device which you connect to doesn't have to be a mobile phone. When you phone T-mobile (or you send a text message to a radio station which invites listener participation) the call (or text) is received by a computer which functions as a switchboard. Phone calls are routed to the headsets of call centre staff while your texts are routed to the radio presenter's computer monitor.