over billed

My contract came to an end in March, I was overbilled for 2 months, when I called the cost centre to query they opened a case and ensured me that I would be credited for the overbilling, they also offered me an option to extend my contract for another 2 years which I accepted. A mail was sent out to me and everything was confirmed. I did not have any service for the whole of May when I called the cost centre to query they said they will investigate and call me back. No one bothered calling me back. After phoning almost every day of the week I was told that my contract was cancelled, the reason is still unknown. I had absolutely no coverage for the whole of May yet my account was debited for R162.00. I would like to know why my contract was cancelled without my consent and why I was billed for service I did not receive? I also recieced an sms on the 30th May stating that I will be credited with R360.00 case reference *** to date I have not received the credit. I will never take out another contract with Cell C or recommend them to anyone as this is just too frustrating to deal with. Please advise when I will receive my R360.00 and if I will be credited for May?