Cancel my contract please!

I cancelled my contract on the 2nd of August. Received confirmation of the cancellation on the 3rd of August. However, I am still being debited and called telling me I can upgrade and that my contract is not cancelled? Not only that but I'm being told now 'call again'. Why am I being treated as though I am at fault when it is an error on your side?

I'm sorry but once I receive a message stating "Please note that the cancellation was processed for 11/09/2023 as MTN Business rules because your contract is ending at 11/08/2023." surely this is now out of my hands and in yours?

Please sort this out and refund me for October.