MTN ****s clients by not stopping the billings

I’m not happy with how MTN handles their customers. I have cancelled my device insurance with them in November 11th 2025 but they didn’t stop the billings. When you email them they ask for an invoice which i don’t have but my bank statement proves that they debited on my account but they say that’s not the proof. When I go to their “self service portal” it says my numbers doesn’t have a linked account, so how must I get the invoice ?.