Contract cancellation

I cancelled my contract with Altech Netstar in January 2015 and I was told I needed 1 months notice which was okay with me, my account got debited. I then asked for a cancellation letter which I received via an email but my account got debited end of February I called it in and the lady that spoke to me had no idea about my cancellation and so I forwarded the email stating my account has been cancelled effective from what date, she was to get back to me which she never did. I called again but this time asked for the manager and i was told that the manager was busy with important calls...... Very dissappointed with the service because to this day my account is still being debited for a tracker that is in a car that I sold in december 2014 already. I would never recommend this company to anyone with such bad service to customers