MTN gave me a faulty phone and they don’t want to responsibility

In January 2019 I took a contract for IPhone X for my son and 5 months later the handset began having network issues. My son went to MTN mall of the north to report the problem and they couldn’t assist , they told him to reset the phone and do software upgrades to which still the phone couldn’t get network. My son went to the store a number of times to which they failed to assist him until he went to Istore when he was informed that the phone has serious defects . In January 2020 I took the phone to the store to get it checked. The store never took the phone to an approved repair center instead a false report was fabricated so that the store doesn’t take a responsibility . I have reported the matter to the regional and head office to date nothing has been done instead I’m sent from pillar to post because they are protecting each other. I have been paying over year for a dead phone and MTN has failed to take responsibility for selling me a phone with defects. My contacts is ***