MTN angry customer

I have settled my MTN account September 2022 and requested them to close the account. Next thing i see an email in February saying i have outstanding fees. MTN are a bunch of crocks. Now its affecting my credit score. I don't know how many times must i tell them i nolonger want to be an mtn customer. So why was there no communication in October and the rest of the months until now February so they can tell me i owe them. Their bill has interests so now they want me to pay them...Nisile. Am really not happy xem.