Poor service delivery

I requested I mifi and router at Telkom, in July 17 they delivered a wrong device, of which they collected and gave me the correct order on the 05th of august however it was not cancelled, basically they added another device, The sales agent who was helping me said she does not know how she will help me claiming that she did everything right it not her fault that I have two contract where I signed for one, been to their shops every week they couldn't help me either for about three months, a guy in amanzimtoti shop did log a call however even if the Number has been cancelled but I have account handed over and they rude collection agents are making collection calls, I now have adverse on my name I guess it will stay there for over a year, my credit profile is negatively impacted not to mention the thought of paying for the device that you are not using but still I pay for it and they refuse to reinstate it even it they have all reference number but even this month month I still have to pay again. I suspect this company has no consequence management