No response after following up 4 times

I emailed Cartrack to let them know that my car had been sold and that I would like to cancel my vehicle tracking. Mariah then rep**** asking for my details so that they can access my details on their system. <br> <br> I gave her the details and asked for confirmation that it has been cancelled... That was at the beginning of March. I've been following up with her and the general client services team since then, but nothing. Instead, they keep sending me bills. Can someone please get back to me, so that I know everything is sorted?