If you paid with a debit or credit card notify the bank of fraud immediately. If you paid at a BOA notify them immediately so that they can shut the account down. Instead of replying to a person who knows less than you, try reading CWG40's or Alfalafa's posts.
Then you are out of luck. Best you can do now is read those posts, file reports, and realize that now that you have paid you are on the easy marks list and will get many more calls looking for money.
IRS Scam:
The IRS does not need to sue anyone. They send you first class letters delivered by the Post Office. Several of them. Ignore those, and they then send certified letters that you need to sign for. Again delivered by the Post Office. Ignore those and they simply freeze your bank accounts and anything else you own. If they can do that, then why would they bother with a court case that might take them years before they get in front of a judge? They also do not bother arresting people for a few thousand dollars for the same reasons I have already given.
Official IRS Government site detailing this scam and providing links to report it:
http://www.irs.gov/uac/Newsroom/IRS-Warns-of-Pervasive-Telephone-Scam
https://www.irs.gov/uac/Online-Scams-that-Impersonate-the-IRS
https://www.irs.gov/uac/Tax-Scams-Consumer-Alerts
https://www.irs.gov/uac/Newsroom/Phone-Scams- ... 6-Filing-Season
https://www.irs.gov/uac/Newsroom/IRS-Complete ... -Scams-for-2015
If you feel you SSN has been compromised, in addition to putting a fraud alert at the 3 credit bureaus, you may want to notify the IRS. Here is the link, fill out the proper form (probably 14039):
http://www.irs.gov/Individuals/How-Do-You-Rep ... aud-Activity%3F