Contact cancellation

Been trying to cancel a contact since March 2020.i have spent hours on hold with your call centre, I have sent emails and I have returned my debit orders since 1 April 2020. I have been contacted by your bot on your Facebook messenger with the same message every time that it has been escalated. Still this contract is not cancelled. Just held in another hour and now I'm told it can't be cancelled because of the outstanding amount. The fact is nothing is outstanding since I have informed you in writing in 9 March 2020 to cancel the contract. I will not be paying the arrears.