MiX Telematics - Contract cancelation

I canceled my beame contract twice telephonically after an agent told me I had an outstanding balance on my account. I kept being billed for the tracker which i was no longer using till to date im still being billed for the devise that I have countless times told them that its no longer in use and they should cancel my account. I have just payed the amount they said I owed them and sent an e-mail to cancellation and no feed back as e-mail keeps bouncing back and call center is a nightmare!! if the call is not cut by an agent that cannot assist, you are holding on the line for hrs. Can you please just cancel my account almost a year of paying for a device that is no longer in use and I'm pretty sure beame can see that.