Nightmare of dealing with Discovery and Tracker

Gave notification to Discovery to cancel their crazy expensive insurance beginning of December 2017 but they ignore it and continued deducting premiums into March 2018, after I complained they then stopped it the debits but delayed to remove their **** tracker device which was more of a nuisance than anything else, calling me each time I went over a pebble in the road. Even though they delayed in removing the **** tracker they threatened to charge me for it if it was not returned!! Now idiots from Tracker are calling me to say I owe them money for the tracker subscriptions which Discovery didn't pay over. Discovery and Tracker have got to be the worst service company ever - charging exorbitant fees but threaten legal action for their incompetencies.