Pathetic Service

My iPhone 6s Plus which is under contract with mtn became blank 6 weeks ago. I took it back to the mtn store(Sasolburg branch) on the 16 March where Elizabeth Maphiri assisted me together with Steven. I was told that since many customers had been experiencing a similar problem with the phone, I'd be given a brand new phone in 2 weeks time. 2 weeks passed without me hearing from them. I called on the 3rd week to enquire and I was told that the phone's model was out of stock. On the 4th week I called again, and I spoke to the manager who then still emphasized on the fact that I'd be given a new phone of which they were still out of stock. Last week when I called the story changed, and suddenly the phone is still in for repairs. It's the 6th week now and I still haven't received anything, I've been told various stories for 6 full weeks.