Unauthorized contract and debit order

I have a bad experience with cell c. On the 03-10-2017 when i checked the bank statement I learnt that there was a debit order amounting to R195 from cell c reference(SP ********** 1 ********** 59). I then contacted the bank to reverse it since it is unauthorized and considering that I never entered into any contract with cell c. Upon that I also contacted cell c and tried to enquire about it, the consultant confirmed that according to their records I have a contract with cell c, but she could not provide details as to what I am contracted for . She then said that i need to draft an affidavit that confirms that i did not enter into contract with them and send to them. The problem that I have is why must i become a victim for something that i do not deserve, for starters cell c is fully aware that the contract is ********** as there are no records in place to confirm its existence , why cant they close it and launch an investigation without requesting me to draft and affidavit. I get an impression that cell c is the one that drives the ********** contracts since they cannot pull records relating to the contract and they also cannot close the so called existing contract that I never signed for. The other strange thing is how did cell c got my banking details cause i never had any contract with them before nor did i furnish them with such information.