Sim swop

Went into store to do a sim swop... CellC to CellC ... firstly i asked if it was possible to keep my Pre-paid number and use my "Contract" sim card, i was told yes... when sim swop was done I just reveived a new pre-paid sim card with my number on... then only was told oh no sorry we can not do that (pre-paid number to contract) anyway i took the sim card (because he couldn't reverse it), asked if i could just keep this simcard then as an extra, will my current simcard still work and i was told yes. Got home and boom my simcard shows not registered on network...placed new simcard in my phone and boom still not working.. been calling CellC and all they can say is that it shows perfect on their side ... i need to buy a new sim card and then they can do a sim swop to the new sim card because my sim card might then just be faulty.... all this for what?? Something i did not want and then nothing works!! I have 3 contracts with CellC and have been a valuble client and this is what you get?? Now i don't have a simcard at all working with my preferred number!!