Cell C
Cancelled itemised billing not cancelled

I canceled my itemised billing for my account, they called me and confirm the cancelation. At the end of December they deduct an instalment for the itemised billing. I query it and customer care "Mary Mazibuko" told me be e-mail, on 2 January, that the invoices were printed on the 1 st of December. I accepted it. At the end of January Cell C deducted again for the itemised billing included. R 207.50 instead of R 186.00.
If it was cancelled why do they still took the payment.
0845616902