MTN charge for a defective phone from day 1

I got a new Samsung A33 on contract from MTN and since week 2 have had continuous problems with this phone. It was swapped in week 2 with a new one, then the new one started giving software issues. It was repaired supposedly and within a week I returned it again. They have now had it for 7 weeks or more and they cannot find the right info, tell me it has physical damage and this and that... I sent it in with a software issue... What the hell is going on. This phone is under warrantee. I have not even had the chance to use it properly but I am paying over 300 a month on it. This is the worst service ever.