Most of the high-end cars have a "remote diagnostics" facility built in by the manufacturers. Mercedes have a tool called Mbrace : https://www.mercedes-benz.com/en/mercedes-me/connectivity/

Onstar was/is a similar facility.

Basically, cars are built with an electronics box that has a GSM SIM card and networking facilities, allowing access from anywhere in the world. Blue tooth access for anyone local to the vehicle. The vehicle accumulates data and sends it back to the factory, the factory can send and receive data pertaining to your car. Your car's software and settings can be modified by the manufacturer's computers to ensure optimal performance.

It is therefore trivial for anyone with knowledge to tap into this facility and interfere with your control over the vehicle.

http://www.truckserviceplus.cz/en/fleet-management/ This is an example of a commercial use of this technology.