When a debt collector:
1. threatens to have you arrested
2. threatens to garnish your wages
3. threatens to put a lien on your home, car, etc.
4. uses foul language
5. attempts to intimidate you
6. demands your banking information
7. makes repeated calls to your home or place of employment
8. claims to be a lawyer
9. breaks any other federal or state law in attempting to collect a debt
DO NOT BUCKLE UNDER AND PAY THE DEBT WITHOUT KNOWING IT IS YOUR VALID DEBT.
In my experience, the more a collector tries to harass and intimidate you, the more likely the debt is not yours or the debt is beyond the statute of limitations.
Furthermore, don't believe everyone who claims you owe them money. Make them prove it, and watch out for scammers who want your banking information so they can drain your bank account. It is easier to take your time to verify the account than to get your money back.