Disgusting

the beginning of July I emailed Cell C to cancel my contract for the end of July the beginning of August they had not canceled my contract and wanted me to pay for another month how I made contact with them and they realized they were at fault so cancel my contract I asked them if there was any outstanding balance from my side which they rep**** no. Now I find out that they still billed me for the month of August and have been charging interest each month. I called them last week and they said they will sort it out and gave me a email address to send the email stating that I was up to date with my account which I did but they have yet to correct this statement and I don't receive any feedback.