Can I be sued for work I''ve done in Florida as a freelancer when there was never a contract?

I worked for a company as a freelance engineer for about a year- recently I decided to terminate services after nonpayment, the response from the company has been not so great. I offered services for the transition under the condition they paid the invoices they owed me. They never responded. The guy sent me an e-mail saying he didn''t agree with charges on the invoice and we need to talk, but when I tried to call him he ignored my calls. He''s sent me some ominous sounding threats and recommended I help during the transition and that it''s in my best interest, but I''m not interested unless he pays his owed invoices. I have a feeling he might have found a line item on the invoice he might try to dispute and say I never provided services or lied. Without ever signing a contract would he even have a leg to stand on? The company is located on the other side of the US so I feel like he might try to sink me with court fees alone, he''s been known to do this before to people.