Cell C - no customer experience - Cancelling of contract that I've never used

Is there anything like customer experience at Cell C? I'm very disappointed. I took out a contract for 2 mifi pocket routers in Nov 2017 at a Cell C shop. Took it back the next day and asked to cancel the contract as it did not work in my area. Since then and numerous calls to the cancellation department nothing has been done. On 12 April 2018, Mfundu Tshabalala contacted me and said that it is all sorted, that I don't owe Cell C any money and that the contracts has been cancelled. To my horror I started getting phone calls from their debt collectors saying I'm owing money to Cell C. I can't believe this. I'm also listed at the credit bureau, embarrassing, this has never happened to me. When I signed the contract I also signed a debit order which was never executed by Cell C because of the process of cancelling the contract. Can someone please sort this out for me. I need a letter stating that the contracts has been cancelled and I don't owe Cell C any money and please remove my name from the credit bureau. The last reference number I've received from Mfundo Tshabalala in the cancellations department is ********** 863. You can check all the calls I made from my cell number ********** 905 this year and from my office number ********** 478. I would appreciate it if this problem can be resolved for me. Very disappointed customer. S P Le Roux (Ronel)