PAYING FOR SOMETHING I DO NOT HAVE

Good day, I need assistance urgently. Last year i did an upgrade on my phone and after 3 months the device gave me problems, to cut the long story short. The phone was still under warranty and I had to be given a new one of which it was out of stock. I then requested for my contract to be cancelled as I was not happy with the options of phones which I was offered in replacement of the initial one. Till today I am being charged more than R400 for a sim, 200 minutes and 500 data, I do not have a phone. I need the contract cancelled which was what i had requested and all my money taken reversed. Thanks MTN