Contract cancelation

cancelled the contract last month , got a call from customer service and a confirmation email stating the cancellation will be effective on the last day of November, but Rain keeps on trying to debiting me on a month to month contract that is billed in advance , Because there is no money in my account now I get charged for insufficient funds, even after sending an email to collect the router acknowleding the cancellation why am am still being debited?Askrain does not work work because all you get is query logged and a promise to get someone to call you which never happens , customer service phone rings forever till you giveup..