MTN data contract

I had a data contract with MTN that expires this month, when I went to cancel it on the 29th of October 2024, they told me that they have already billed me for November by the 27th of October. They said they are not able to cancel it now, that I was suppose to give them 30 days notice even though they knew that the contract is expiring by the end of this month. I had no agreement with them to bill me for November as my contract expires at the end of October. They said this is how business works.