Bad Admin at Mix telematics

I have actually cancelled my contract for a Beame tracker with Mix Telematics in April 2023. I still get sms's and emails and invoices from them about outstanding monthly payments. I have called numerous times about removing me from their system, and yet I am still being inundated with irrelevant and annoying correspondence. They even deducted a monthly payment from my account in August. This month I had a woman call me about my unpaid account .... I explained for the umpteenth time that I no longer have a contract with them and please to remove me from the internal automated system. I have 6 different case numbers from support over the months. How difficult is this ?