No tracker in my car but i must pay

They installed a tracker in my BMW car and the next morning my car wouldn’t start, i called them to come fix it, they installed a new one. The next day it did the same thing. When the guys came i told him to remove the tracker completely and cancel the whole thing cos clearly it was no use to me. I received a call the guys had requested for me and canceled everything with a lady on the phone. She advised it was all cancelled.

2 years later I receive a call saying i owe your company. Please advise of what services did your company provided that i must pay for?