missing airtime

I took out a contract with cell c a few months ago but ever since whenever I load airtime on my phone it disappears... My free minutes, my sms's and my data as well as my airtime disappears. I have tried calling them to resolve the issue and they have informed me that they would give me feedback regarding the matter in 24 hours... That was more or less a month ago. Its a waste of time and money. Cell c is a good network with bad service...