Cell C has continued to try and charge me AFTER I have already cancelled my membership and payed off all outstanding arrears

Cell C has continued to try and charge me AFTER I have already cancelled my membership and payed off all outstanding arrears. They even sent me the acknowledgement of cancellation email. The only time customer care bothers to contact me is when they think I owe them money. All other queries or requests are just ignored including the email I sent confirming all arrears are cleared with proof of payment. I would not recommend anyone who wants a professional experience to sign up with Cell.C.