MTM cellphone contract

I had a cellphone contract with mtn since 2022 February. It was 36 month contract for Huawei nova 9 paying R523 for 2 handsets. To my knowledge, the contract ended in February, I contacted mtn in February and made a notice for cancellation and they agreed that it will be terminated end of February 2025.

To my surprise I'm receiving the SMSes informing me of the installments of R368 *2 which is R736.

I know that may lead to them handing my accounts to debt collectors which is unfair.

I don't want anything to do with mtn contact anymore