These guys are clearly runnign a scam. Do not co-operate. Report the information to your State attorney General's office of consumer affairs fraud division.  FBI agents will not call you over the phone attempting to collect a debt, etc.... they are trying to scare people into paying. If they are legitimate they will be willing to submit information in writing to you concerning your debt so that you can dispute it and they should also be able to provide you proper business information so you can verify their claims. This is a scam.