CellC is still debiting my account after the account has been closed!

My 24 month contracted end with Cell C & I called Cell C during October & requested for my account to be removed from the month-to-month contract system (which they put me on -with out my permission!)I was told, I had to settle the account in order to do so, I paid the R199 to settle it. Today I was billed again by Cell C. When I called them, I was told that I would be billed again until the 1st of December, even though I requested the account to be closed during October.