Cartrack not trustworthy

I asked cartrack to close my account after I had finished paying if off and asked for a letter stating that is fully paid which was sent but the account closure letter wasn’t sent. Three months later im still debited from an account I hardly use and it bounces which will cause a fee cause there’s no money and its ruining my credit score cause by the way. Ive sent Cordelia and Elrina (consultants)WhatsApp and email regarding this matter and nothing seems to done .