Mobile number hasn't completely switched over from carrier to iPhone

I have had my iPhone since December and it was unlocked as I bought it from the apple store.

I set up a contract with the network 3 and then used my PAC code to transfer my old number over to my iPhone.

However this only partially works as under my contacts its still lists my phone number as the original number that my 3 contract had when I bought it.

If people text or ring my old number (the one I want) it still works but when I reply or ring someone it comes up as the number I don't want!

So I effectively have two working numbers?!

I don't know how this has happened but I just want my original number that I transferred as my number.

I have seen this similar question on an apple forum before but the only reply was to turn imessage on and off and then turn off/restart the phone but it makes no difference.

Please Help!