Bad service

Bought a Nokia phone @ incredible connection in Secunda on the 18th of Feb ,and on the 23 of may the phone died all of a sudden ,took it back for warranty they sent it back for repairs 2 weeks later they told me the phone wasn't repaired cause I was using an MTN sim card ,of which I rep**** why I wasn't told I about this the time I bought the phone . Fast forward a month later they sent it back for repairs but still didn't get the phone ,and I had to call them a number of times just to get a response ,finally they told me the phone is back and its beyond economical to repair ,I said fine since its on warranty replace it, they said the are not going to replace it I should come collect my phone , I called their customer line they said they will call me back within that day that was a Friday ,I waited for the call that never came they finally called me on the Monday and asked if someone had called me and I told them no one had called me and the person just said ok and dropped the call ,till today I haven't had someone call me to help me with my complaint,i have the worst service in my entire life how can you just think its ok to sell something and say it died so f**k off