Tracker - Service? What service?

I sold my vehicle which had a Tracker fitted. I informed Tracker and I received a letter of confirmation dated 2 Nov 2021, that the account has been cancelled. I was told during my original phone call discussion that no further debit orders would be effected. Yet, come end November they debited our bank account again. I emailed an inquiry to *** on 4th Dec and received an automated response with the message "Your work item number is ***4" , but no-one has subsequently contacted me in this regard. I keep getting sms messages that Tracker has tried to contact me but I see no record of missed calls on my phone nor any emails from them. It is because of this type of incompetence that most people dislike signing for debit orders.