Simcard not working

We call to find out what the problem is on our contract *** On Monday morning the phone still received calls and sms and later the day it keep starting to search for network. If you place the sim in another phone the sim still not response. We holding on for ages and no response. We send a mail and then they just say for accounts send your message to .... for enquiries send it to ... and so the email went on and no definitely answer what is wrong. Another service provider advise that some ***** is going on so how do we stop it if Cell c is not willing to assist us.