No service on new three IPhone?

I got a new IPhone 5 from 3 yesterday (I upgraded from a galaxy ace) and my new sim card isn't working 30 hours later, the man in the shop said it would take a maximum of 24 hours. Is there something I need to do to make it work or are they just taking longer than they said they would?

Hello Sean i think its time to phone 3 network they should be able to sort the phone there and then over the network.
But before you do this turn the phone off and then on again… This may be all you need to get the phone registered on the network.