Fed up with Mtn and Mondo run around they give me

Had a contract with Mtn and I was called to say that I need to renew it. Which I did but when I received the product I was not satisfied with it then returned it through one of the stores close to me. Only then I realized that it was a Mondo contract of Mtn. I still pursued the cancelation in that case. Mondo confirmed receipt of the product but now Mtn is not stopping to debit me. Every month I must reverse their debit order where now the banks are charging. Mtn says that I must contact Mondo and Mondo on the other hand are saying that they are looking into this matter. Mtn shared my contact details with Mondo without my consent as the contract that I had with them was a walk in and not through a 3rd person. Now in this country we have a POPIA Act that is applicable. I want Mtn to comply or we can take this thing further than being hoodwinked by them. These monopolies should be controlled.