Payment Problems

I had Tracker in my car. In 15 October 2014 I was Retrenched from my work. I paid my Tracker up to the end of January2014 but I canseld my Tracker at the end of October 2014 by phone. Tracker let the acount carey on after January2015 and now they whant me to pay it. I lost my Job and I did cansel the Tracker and paid up front. I lost every thing I got in live an they just whant. Its there mistake for not canseling it I can not pay if I dont have any Income. They handed me over for collections.