Unhappy client

On the 28 August 2019 I was offered an explorer decoder over the phone and I took it. After they delivered the decoder I wasn't happy with, I then told them to send their people to come and fetch it. They did not come until today, but they are continuing to take R139 from my account.

My worry is they will blacklist my name if I reverse the money they are taking, and send my name to credit bureau.