Telematics appalling credit control department who send Bill's for cars I dont even own

October 2021, I bought a new vehicle with pre purchased Beame for three years, but telematics keep sending an invoice for the old car which has been sold, they keep on sending me messages to settle the account every month, I have called their cancellation and debtors department and they keep on saying they will rectify, since November last year, and this week their phones ring unanswered, I am flabbergasted by their unprofessionalism, how can I trust them with my car if they can't handle their account department