Afrihost cancelation process.

Begin June I contacted afrihost to cancel my fibre connection as I was moving. Their contract is cancel anytime, by the way. Firstly it's a nightmare to find where and how to cancel and the options are dismal. Eventually with the help of another agent, I got it cancelled. 8hrs later they do a debit order for internet I cannot even use, their reasoning, I should have cancelled at the beginning of the month, I've receipts of proof of conversations at the beginning of the month. They refuse to reverse the debit order. However if I **** and cancelled in a different manner, they would give me a month free internet. How does that work?