You are the victim of a well known scam, and yes, if you believed the pop-up that said your computer was infected and paid for those services, the people you paid the $250 to have caused your problem.
Here's how the scam goes: You get a cold call, unsolicited email or computer pop-up from a supposed computer tech company, usually, but not always claiming to be associated with Microsoft/Windows or some other important company and telling you that your computer has bugs which they can repair for you. What these folks are looking to do is to is to get remote access and/or to install malware which would allow them to hack into your computer, phish for passwords, get into your accounts and rob you blind. Additionally, they'll get your credit card number and may commit further identity theft.
Allowing anyone or any company into your computer or downloading their software without fully vetting their reputation first is a good way to get hacked and to give an unscrupulous person access to all of your accounts. So if you granted these folks remote access or installed programs that they gave you, first and foremost you need to take precautions against identity theft.
I see that yesterday you talked to a tech person on this site. That's fine, because our techicians are independently verified and are who and what they say they are. If they walked you through a debugging of your computer, great. Just go and change all of your passwords and pin numbers.
If you didn't ask them to do that, take your computer to a local reputable computer tech shop and get your computer debugged. Or you can post another question in our computer category here on justanswer.
Just running her anti-virus program will not be enough to prevent possible hacking, because malware can override these programs. Once the computer is debugged, change all PIN numbers and passwords, as I mentioned earlier.
You should also monitor your bank and credit card accounts carefully to look for unauthorized use of your bank account or credit cards. If You paid the company via credit or debit card, YOu need to report that card to your card carrier as being compromised, close it and get yourself a new one. Ask your card carrier to do a chargeback of the $250