Poor service

My network has been giving me problems since 19 Sep 24. When I check balance it gives me a code " connection problems or invalid MMI code" called MTN consultants 3 times, they all said different things and problem was never solved, the last one said they will escalate my problem and it should be solved in 48 hours, today it's the 22 Sep 24, still nothing. I can't even buy DATA the phone has actually became useless because I'm using USELESS network "MTN" even during the month of Aug I experienced same problem. My ID number is ***