Been billed for cellphone i've never used.

I took out a contract in May 2015 over the phone and the consultant assured me that the Microsoft phone that she sold to me is not similar to the Nokia Lumia. When I received the phone on the Friday I was so disappointed as it was not as I was expected the phone to look like. She said that if I was not happy I can return the phone within 7 days. I returned the phone to MTN golden arce Cape town on the Tuesday. I received a \reference number"at the store but in all my further attempts to solve the issue I was told that this is not a proper reference number and does not reflect on the system. I gave them the device that day and MTN has been billing me every month since then. I am FED UP. I\""ve send emails to summer mobile and MTN but till today nobody has taken accountability or even try to attempt to solve my problem. It seems that they are eager to take MY MONEY but cannot provide me SUFFICIENT CLIENT SERVICE."""