A fairly common tactic of shady debt collectors is to tell people that they will go to jail if they do not pay a debt. I've even heard about debt collectors impersonating the police and telling unsuspecting people that they have a warrant for them and that they will be arrested immediately unless they pay their debt.
You cannot go to jail for not paying your debts. Period. Any debt collector that tells you otherwise has violated the Fair Debt Collection Practices Act (FDCPA). The FDCPA prohibits false and misleading representations when attempting to collect a debt. This prohibition specifically includes telling you that the nonpayment of a debt will result in imprisonment.