Unauthourised debits to my account

The productshop has been debiting my account for the magzone and safeguard products. I understand from them that they offer value added service products to MTN Yello Mobile clients and they gave me the cell number which is *** as well as a reference number which is YM-***6-1.

The problem is that I neither have a contract with MTN nor have I authourised MTN or any of their partners like the Productshop to debit my account. I have called MTN several times on ***and ***. No one seems to be able to or perhaps not interested in assisting me. I need someone to assist in resolving this issue ASAP!