cancellation of telephonic mobile agreement

I've accepted a mobile upgrade on my MTN contract via telephone on Monday the 03/08/2015 and received it on 06/08/2015, but it was not what I thought it to be and on contacted MTN to explain that it is not what I wanted and I need the phone exchanged. After numerous call centre consultant referals I was finally advised on the 07/082015 that I can actually exchange it at any MTN store. When rocked up at MTN Zevenwacht Mall on Saturday 08/08/2015, I was told that is not an option, so I said in that case it want it cancelled and returned so took the phone and send a notification to the company who send me the phone to collect it from them. A week later I inquired about the cancellation but nothing was done, so I gave it another week and than went back to Zevenwach Mall to make further inquiries and what do you know the phone is still there and another request was send through. I than found out that the people who phoned and issued me the phone was Velociti so I phoned them and gave Sumaya Smith the details of the query and request them to collect the phone form MTN Zevenwacht Mall. Ever since I kept phoning to find out what is happening and the phone is still with MTN to this day.....