Worst service

I have been with cartack almost a month. Worst service i recieved First they did not pitch up on our appointment to install device.I had to phone after them to get a new appointment. Tested my device on 30/07/2020 waited 15 min for them to call and no response from them.

I asked to cancel my contract as i cant rely on them and they want to hold me liable for cancelation fees.How can i trust them with my car.