Frustrated with the incompetence of credit controllers!

I had an adt account, which I attempted to cancel in July 2019. I sent them screen shots of my attempt to cancel, which they ignored. In August, I emailed them again. After going through various emails and telephonic conversations for the past 5 months, they eventually acknowledged my wish to cancel. After much deliberation, they agreed to refund me - Despite disagreement on the amount to be refunded, I accepted, because i just wanted the matter to go away. I eventually received the refund and the acknowledgement of my account being closed... Then surprise surprise... another debit order was taken off my account in November. I have emailed the credit controller who acknowledged that I needed to wait until the 20th November for my money to be refunded. No sooner to me receiving this email, she sent me another stating that the money is not due to me. I am not sure why I am liable for a debit order to be paid after my account was officially closed.