No communication no feedback

Hi there my vehicle has not reported the correct location for about 2 months I want to cancel and i am told m still liable for this and next month debit order . This is unfair as the unit is not working and its not affective so what am i paying for. I have sent emails no response and you still debit for no service. Where do faulty notifications get sent ? how do you not know this device is faulty ? I want to cancel my cover with immediate affect the service is not up to standard.