Awaiting a credit since October

Set a limit on my account including subscription the idiot who took my call didn't include the subscription so got billed R600 more than I should of. I enquirered about it and cell c went back and listened to all my calls and agreed that I asked for the subscription to be included they agreed to credit my account and I am still waiting every time I call I have to open a new query as they try call and god forbid they don't answer they close your case. I'm sick of the customer service and lack of effort to fix a complaint I have had enough