Been trying for months to get them to cancel my contract, but they won't. I've called and emailed and they don't respond They keep debiting my bank account, and every time I write back the debit order it costs me money I think their service and administra

Been trying for months to get them to cancel my contract, but they won't. I've called and emailed and they don't respond They keep debiting my bank account, and every time I write back the debit order it costs me money I think their service and administration is very poor What can I do to get the necessary attention