Complain on MTN contract

I had a contract with Mtn since 2019 towards the end of the year, 2022 I tried to close it since it was supposed to end, I tried to call with no luck then I sent an email hoping they will respond but they didn’t until I did a follow up few days after that email, someone responded asking for my details and I provided them and I have those record but she/he never feedback after. Then this year January I’ve trying to get hold of them sometime I will get someone but after hearing my story he would tell me that he can’t help me. They been transferring me to different department but none of them was helpful. Someone from customer care suggested that I report via email and I did that but still I haven’t got any assistance. The sad part is this my account has been handed over without any communication but I did try to communicate on my side. The sad part is that this is ruining my name I now have a bad credit record because of MNT. Please help me to solve this issue