Contract retention and bad customer service

My contract ended in December and I decided to make it prepaid. Firstly they debited the wrong date and my account was in arrears. I didn't realise that they didn't debited again and when I phoned in November they said they are not able to make me prepaid once the full amount was settled. I told the consultant thta they could debit the full amount on the 1st of December. On the 15th of November they debited my monthly fee which I didn't authorized. On the 30th of November they debited my arrears amount and my monthly bill. On the 1st of December they debited again the arrears amount and the monthly bill. I phoned numerous times to make the contract prepaid and as soon as I get transferred to the retention department they end the call. Today the 7th of December I tried once again. Same thing happend. I eventually got through to the retention department where a friendly lady helped me. She said she made my contract prepaid effective 7 January. Now I still have to pay another months full bill payment, because I didn't give 30 days notice. Best of all I have to pay a full bill and they take the remaining minutes and data on the 7th of January. Cell C. Really! Your customer service agents are very rude. I have to repeat all my details I don't know how many times just for them to tell me they will put me through to the correct department. I have been a loyal customer for many years. It seems like you don't want me to cancell my contract and now aI have to pay for it. Not to mention the bank cost I had to carry because you debit whenever you like. Why did I sign a contract?