Cancellation of Contract

i bought an samsung A3 with mtn bedford centre and i kept on going back to them telling them the phone doesnt pick up network everytime i switched it on and i also when i get a call the phone rings 3 time before it can reach my handset and constant freezing of the phone was the issue. they recalled my phone and sent it back on the 15 of March till today i haven't received feedback and on the 5th of April i decided to cancel my contract bcoz i didnt have a phone and i wont pay for what i dont have on hand. i still dont get any feedback this morning my phone was credited with minutes and i specifically told them that i dont want their minutes bcoz i dont have a phone to use those minutes and data. This morning i sent an email to complaints department demanding to get the number of MTN owner of Bedford centre and suddenly the store manager responds with a reference number only today i've been waitng since March for it. their service is pathetic and i dont want to set my foot in their shop. They dont respect their customers and they dont give feedback at all. i would like to bring this to the owner's attention that his business is not in the good hand.