I have no contract with vodacom but every month, there is a debit order that goes off with vodacom reference

I have no contract with vodacom but every month, there is a debit order that goes off with vodacom reference. I then called to find out, they told me they are investigating, they will revert. All I want is them to stay away from my account, everything I reverse that debit order it affect my credit score negatively.