Consistent Harrassment From Cartrack

I have had it. I recently installed CarTrack, and ever since I have been inundated with phone calls from their agents trying to upsell me on more products. I did my research before signing up, and chose what I knew I could afford. I have asked, several times now, to be left alone. Especially because my mother died recently, and they were harrasing me even then. I cannot live like this. I cannot sign up for one thing and get harrassed in return. I will be pursuing how to withdraw from this contract on the grounds that I am being harrassed, and that this harrassment is negatively affecting my quality of life.