Overcharged for 3 years!

I have canceled 2 contracts with Telekom 3 years ago. And for the past 3 years they have still charged me every month to keep it active. I have been out of the country and was not able to sort it out from abroad. Last month I went to a Telekom store to cancel those contracts again, and instead of canceling, they reinstated the contracts. I also went to renew a contract with them with a much cheaper package, but they kept me on the same package as before and charged me twice for subscription fees. So now instead of paying R259 I am paying almost R900 and no one in store is able to help me and the billing department is also not getting back to me. There is no way to stop these payments from my side without getting black listed