Still waiting for my refund since August

On the 25th of August, you made payment for July's invoice/services, and on the 1st of September, the payment was for August's invoice/services as you changed the debit date from the 25th to the 1st of every month. Your billing is post-paid, meaning that you pay for a month's service in the next month. Invoices for a month's services are generated at the end of that month and are due in the next month on your set payment date.