Mtn is refusing to fix my phone

Good evening all, I trust you are well. I bought a Nova 5t from MTN Northgate in June 2020, it had a free 3 months screen replacement, the screen cracked and I booked the phone in on August 28 it came back to mtn unfixed 4 weeks after I booked it. It was within the 3 months of free screen replacement when I booked it in. I took the matter up to the line manager and he promised to escalate the matter to his seniors, I went back to the shop last week Monday and he informed that he is still awaiting feedback, I went back again on Thursday I got the same answer, I went back again today and have decided to take back my phone because it's been long overdue. Inquiries are only made when I am at the shop. Please assist me with this matter.