Contract still not canncelled, being billed twice monthly

Good day

On the 19th of August I called the call centre upgrade and cancellations line to cancel one of my contracts which was due for an upgrade. I was then told that it takes 30 days for the cancellation to be complete. I then called in September a month later and was told its cancelled. Two weeks back the line is still not cancelled and I'm billed on a month-to-month basis placing my bill double what it was supposed to be.

I then called in again and was told to rather go to an MTN store which i did but was told to call again the retentions centre. I called yesterday and was told the consultant who originally started with the cancellation forgot to close the whole process. My biggest worry I followed the correct process in cancelling the contract yet i was double billed for September and October whereby the contract was supposed to be cancelled.

May, someone please assist me with this issue as i am really disappointed with the fact that someone else made a mistake by not completing the process on their side and I have to suffer by fitting the bill yet i followed the correct procedure in cancelling this contract.