I was reading some testimonials, they don’t use the built in Windows remote control thing to access your computer they use something else, were you paying attention when they were working on your system? If you could uninstall whatever they installed or reset any of the remote desktop setting they used, that should stop it.

Last resort will ask for the resident malware removal expert in this forum to look at your system to reset any remote desktop settings or the iyogi software enabling them to remote connect. It is free and they DO NOT need to remotely control your computer to.