Kobekay,
First of all, DO NOT send them any more money. In your post you mention that you don't know what the debt is for or who incurred it, and you don't have to give anyone money just because they say you should. It's up to them to prove you owe.
If the collector told you that he could simply call your job and have money taken from your paycheck, that was a lie and in direct violation of the fdcpa. No collector may make false statements to a debtor, and especially not false statements involving action against the debtor. If the collections agency were going to garnish your paycheck, they would have to take the proof of your debt in to civil court, and have a judgement against you to do so. There are waiting periods of up to 90 days involved, wherein the collector must prove that you have no intention of voluntarily paying the debt.
The collections agencies know the laws, and it's a good bet that if someone calling you claiming to be a collector is consistantly rude and hateful, they're running a scam. If they refuse to send you your account information or tell you details about the alleged debt, it's probably a scam. It's required by federal law for collectors to provide you with any and all information concerning your debt that you request.
If you have the name and address of any collections company, look them up BEFORE you ever send them any money. Check them out, make sure they are a legitimate business. It also can't hurt to call the original creditor and ask them if they sold the debt, and to whom.
It's fully within your rights to report any collector the instant you feel you have been abused. The FTC doesn't mess around with them, and they take all complaints seriously.
I strongly urge you and anyone else who uses credit to become very familiar with your rights and responsibilities under federal law. There have been a lot of changes made in recent years, both at the federal and state levels, and the government is trying to crack down on scams and abusive collectors. No one has the right to speak to you with anything other than respect.