I agree with @polynomial, this sounds like a scam. Facebook would never call you, there's no such thing as a Facebook tech. Do not pay them any money! It could be that your computer has been infected and that you are getting pop-ups telling you that your computer is infected and you need to call a number to get it fixed, this is also a scam where they sell you a fake AV tool that will remove the so-called virus.
If someone has called you out of the blue then tell them to take a long walk off a short pier. Make sure your computer has all OS updates, Adobe updates, Sun Java updates, etc installed. Also make sure you have an antivirus installed and it is up to date. Microsoft has a free one that is actually pretty good.
If you have pop-ups on your computer telling you that your computer is infected by a virus, then it is. The virus gives you a pop-up telling you your computer is infected in hopes you'll fall for the scam. The only way to recover from this is to re-build your computer. Get a portable hard drive and copy your important files to it, then completely re-install the operating system. Make sure it has all the updates on it, and an Antivirus program. Use the AV to scan the portable hard drive and if it is all clean then copy the files back.