Mtn canceled Billing

why is MTN still billing me because i have paid and canceled your services 5 months ago? I keep on being debited every month ,i called them to find out why am i still being debited they just said for that if for services rendered to me and when i asked them which services no1 answers me because i paid and canceled my contract mid october. What happened was,i called mtn and i told them that i want to pay whats due to them for my 36months contract. They told me the amount and i paid and and their employee suggested i cancel it month end then she scheduled cancellation on the 29/09/2023. I also received an sms telling me that the contract is scheduled to cancel on that day after they deducting their services rendered money for September. Come the 29th it didn't cancel,i wasnt aware of it because i received an sms telling me its cancelled. I received data on the date where i normally receive them ,i called and they said the i owe them money. Then i asked what money coz i paid up my phone. The lady also seemed confused because it was reflecting to them that i paid it all up. Fast forwad they canceled it but im still being charged for "services rendered " ,i dont even know which services rendered because I canceled those services and the money keeps increasing. Worse part is i keep on being sent smses that they have sent me invoices but i never received any invoices because the email they are using is not mine at all and even when i called them to change it they never did. I am Sick and tired of mtn charging me money i dont understand why and how since i canceled my contract and paid it off a long time ago and no1 is willing to explain to me why and how? MTN BILLING better fix this mess they have made. Mobile number ***