renes,
If you haven't spoken to them again, I would wait for the next call. While laws differ from state to state, I have yet to read the article about someone who was arrested over not paying back a loan.
What they can do is sue you in small claims court, win a judgment, then try to garnish your wages, but somehow I have the feeling that companies who use these tactics won't go through that process.
If the loan isn't legitimate (i.e. you don't have one outstanding), I would trace the call and report it, as it could be a scam to force money out of you. If it is legitimate, I would go to your lender and work out a payment plan with them.
Depending on the state, once a loan goes into default, they are limited to collecting only the principal on the loan and not the interest. It's still a hit to your credit report, so I don't recommend it, but it may be an option where you live.
Check with the local/state laws before proceeding so you are aware of your rights in this situation.
Good luck.