shocking service with MTN

I upgraded my contract on the 19th January 2018 , the call centre agent clearly didn't listen, when I asked to be contacted on my cell and not the tablet no. that I updated, after many calls I received the wrong devise on the 6th of Feb 2018, which I returned on the 7th Feb 2018, today being the 12th March I have still not received the device. I contact the call center on a daily basis and the consultant always informs me that she or he will email the lady who assisted me to call me, she never calls and neither does her supervisors. Nobody at MTN can give me a straight answer, but I will bet if I ask to cancel the contract, quickly I will be given a list of rules why I cannot cancel. then my next mission will be to reverse charges for device that was not in my position. im looking forward to a response to this shocking service.