Incorrect billing/ inaccurate billing/ Unauthorized Debit

December 2017: Cell C did not debit but double debited the following month. February and March 2018 Cell C debited more than 3 times on my account with different amounts. I reversed the other amounts that I was not aware of.

And now Cell C collection department keep calling and asking me when will I pay the money owed to them. I have asked them to send me the full statement that has a clear number/and amounts of the calls made,data used, amount debited and amount still owed. If there is any.

They failed to do so and only told me that they do not know anything. So how can you collect a payment if you do not know how much has being paid?????