Card reader wont read new sim

A

AC Question

I took the contract sim out of my sony experia when i upgraded phone but now the experia says card inserted .restart phone but when restarted it says no sim inserted.
Its a brand new sim on the same network as the contract.
Called 3 who told me to leave sim card in phone and it would work.....it dosnt.
Could it be the sim card reader is faulty even though the phone shows "sim inserted ..restart device...upon restart it still says insert sim...its as if the phone knows a sim has been inserted but dosnt read it.
Thank you