Xperia Z3 :: Phone Not Registering On Networks

My service provider is Three UK. I'm currently on a trip to Switzerland where my screen broke, and after being screwed around by the Swiss repair factory that Sony uses for three weeks, I've finally got my phone back, except now it's not connecting to the available network (Salt.). The networks show up in the list of searches, but after spinning on "registering on network" for a few minutes all I get is the usual "can't connect to network, please try again later" nonsense. The wifi works, however. I've tried repairing it with Sony Bridge for Mac, still nothing.
 
When I had a Z2 I had a similar issue once after sending it off for repairs for a broken screen- the repair people dinged up the internal antenna during repairs and it wouldn't connect when it got back. I sent it off again and they fixed it. Could this be the problem now, even though the wifi is working? I have a flight back to the UK in a day and I don't have time to send it off to the same company.