End of contract

I had a contract with MTN and it ended about a year ago so they decided to continue with a month to month which I did not have a problem. On the 20th of March 2026 I told them to cancel the contract as I'm no longer interested in it so they logged a notice saying they will cancel it after the deductions end of March, so the money was deducted and due to the agreement I expected the contract to be canceled.... To my surprise I got a message that I'm owing them 2 months installments and I've been put to their collection department which I've been trying to get hold of and the phone is not picked, I've been holding for about 30minutes now.