Cellphone under warranty

I did my cellphone up grade and got the new Samsung S7 edge on the12th of March. . You have a 7 day fault report. In which i phone on the 17th, 18th, 19th and the 21st of March which still falls in the 7 day fault report. I phoned on both the numbers *** and Cell nr *** numerous times in which i got no answer from. When i went there and told them they said i had 7 days. I told Lerroy i have been phoning and phoning and no body answered. The new S7 edge had been over heating while i use it or when its in my pocket and its the device fault. So this is not my fault of problem, its MTN. I am very very disappointed. My phone has been sent in now lats week saterday and its a week later and stil no feed back on whats going on. This is very bad service.