Can't make, Receive calls or access 3G

Yesterday I left my iPhone able to make calls and use 3G. When I went to sleep, I made no change whatsoever to the phone.

Today when I woke up, although the network appears in the top left corner "vodafone etc.." with signal strenght, I can't make any calls or access 3G.

I asked for a new SIM CARD which still doesn't work. I tried this new SIM CARD in another iphone (5) and it works perfectly.

I had iOS 8.0.2, already updated to iOS 8.1 and the problem persists.

I did not drop the phone, didn't slam it against anything.