Premium deduction after cancellation (for 27 months); no feedback and no refund

I wish I could rate them with a - 0. We send the cancellation request on 23 May 2018 as the car was sold. A agent emailed us back and confirm that a agent will phone us regarding this. After no call we send them numerous emails and called more than 5 times. When we looked at our bank statements a while ago we saw that Netstar was still deducting premiums from us. I have tried calling them but the telephone number does not work. I emailed them on 31 August 2020 to cancel the tracker and demand pay back of the 27 month of premiums. On 9 September they emailed saying our cancellation has been processed and the credits apartment will phone us regarding our refund. To this day no one from Netstar has phoned us regarding our refund. I send emails on 15 September and today again. With all of them I have received read receipts. I have never work with such bad and pathetic customer service in my life! Would not recommend them to anyone!