Hi there and welcome
It does sound a bit suspect.
Do you know the name of the software they installed?
Ok it is not any security software, likely it allows them access to your computer
We will need to uninstall it asap
Which version of windows are you using?
ok, then it is easier to remove.
Go to Finder, Applications.
Send the application to Trash
Then empty the Trash and this will remove it
Tell me when you have please.
because it is a common trick used with the wording anti hacker as the software.
There is no actual security software called this, it is a script they read off and why I see it from a lot of my customers here
You only need Sophos on your computer for security
If this is the software they installed then trashing it will remove it from the computer and then stops any access to your computer.
They need the software in order to access your computer, once it is gone it stops it.
If you want, for an additional fee, I can sign onto your computer and check for any other suspect software that has been installed.
It is optional, and I made the offer, so if you wish for this, please accept it.