MTN: Rewards sections massive failure

I'm am extremely upset about the poor and pathetic service from MTNs Rewards section. I was given the chance to try out a product with the promise that if I returned it within a week I wouldn't be charged a cent. I returned it the following day of receiving it and have been charged the full amount for the product for the past year. After calling the call centre every month since and been repeatedly told it will be escalated to a manager and I'll be contacted thereafter I never was. Extremely pathetic! Now I'm being contacted by Nudebt and told I refused to pay my bills??!! I was happy with the service in your BlueRoute mall branch and even they tried their best to assist but the same things are being told to them. This is completely upsetting, my phone is no longer active and it's even affecting my day to day business, I was even denied a loan because of this debt, it's extremely ridiculous. I can no longer contact the call centre at this point because of the sim being blocked and nothing can be done at their branches. I could never recommend anyone using MTN again because of the poor service.