MTN debit orders account even after cancellation

In February I was contacted by a salesperson from who I originally thought was an MTN call centre. She offered a new product with an extra SIM and whatever amount of data for whatever amount per month. As my husband uses the contract I handed the phone to him and he agreed to the extra service. Details were provided and the contract agreed to. Later my husband decided he did not want the extra contract as he did not want an extra SIM. I sent an email to MTN's cancellation the next day asking that the new contract be cancelled. I received a mail back saying my query was being attended to and given a reference number. The mail also said I'd hear from someone within 24 hours which I did not. Comfortable I had done enough to cancel the contract I left it until the extra amount went off along with my regular debit order at the end of March. I called the call centre and was told that a third party had sold me the contract and that I should send a follow up mail requesting feedback on the cancellation. Also, I had not received the SIM as when contacted by the courier i told them i had cancelled and that they should send the SIM back to MTN. I sent another mail got the same automated message. Heard nothing within 24 hours called MTN again and was told I had to contact the 3rd party as MTN did not sell the product. I sent a follow up mail and again was told it was being looked into. At this point i have up to 4 reference numbers. Nobody contacted me. Now end-April that extra amount has gone off my account AGAIN. I called MTN call centre again today and was given a number to contact the 3rd party and surprise surprise the number doesn't work. I'm not sure what more I can do. MTN call centre agents wash their hands of me as the product was supposedly not sold through them and I can't seem to get a hold of this mysterious 3rd party. Why is MTN giving my Information to 3rd parties anyway? What about protection of Information? This is poor service. I suggest you don't accept any MTN products from someone calling as you don't know who's actually calling. How am I going to get my money back? I can't reverse the debit order as it's just been added to my existing debit order. I'm so mad!