Putrid service from MTNGreg

I purchased a brand new cellphone on 20 August 2019 at sportscene in the liberty promenade shopping center in Mitchell's plain. On 1st May 2020 I handed the phone in at the store as it was dropping calls and reverting back to the home screen when using an app on the phone. The lady at the store advised me that the phone will be sent to MTN to be assessed. A month later I received the phone back as there was a misunderstanding between sportscene and the courier company. A day later I returned the phone to the store as the same problem was still happening with the phone. The phone came back from MTN the second time with the same problem still happening. I am about to return the phone for the FIFTH time as it has still not been repaired. The staff at the store as well as myself spoke to MTN and the supervisor(name known to me) advised that they can not replace the phone as there is a process to be followed. Still waiting for the process to be explained to me. On my way to return the phone for the FIFTH time. Lost for words and not sure how to explain this service from MTN.