Unfixable phone

In a week of purchasing a Nokia lumia 1320 it started over heating freezing and wsitching off on its own I had this problem reported by Edgars and was transffered to repair centre by Eastgate aftr 5 working days I collected my phone and it came worse than it was by this time it was heating up to screen blank freezing through windows I reported this by Edgars to have my phone replaced for a new device or exchanged for an upgrade I was thern trasnffered back to the Vodacom repair and made aware that this was a second time and the phone was new after 15 working days I received my phone on the day of collection I switched it on and it was heating up and made this aware to the consultant only to find out my phone was not fixed and they told me nothing was wrong after 3 days of collection I returned the phone and in its unfixable state I feel its unfair to cotinue with payments to my account for a brokern phone its a month and never used my phone for both Vodacom and Edgars if nothing is done in time to assist me get a new device this will be a court case very ****ed customer