Contracts aren't just in writing. There is a contract involved. Oral and "implied in fact" contracts (based on the parties' conduct) are just as enforceable as written and signed ones, although they're harder to prove and sue on.
Small Claims court may be your best option. Before you decide to sue, send the company a demand letter for amount they owe you to their corporate agent for service of process, which you can look up on the CT Secretary of State's website. Send it by certified mail, return receipt requested, or by FedEx or by registered email (www.rPost.com) so they know you're serious and you can prove receipt. Give them a deadline, a week or 10 days from their receipt to pay you or you'll have to sue them. If they don't pay you by your deadline, follow through and sue. Your letter might also threaten to report them to the BBB, Ripoff Report, Yelp, Epinions, and to post this incident on your Facebook page.
PLEASE READ THIS BEFORE YOU COMMENT, EMAIL ME OR PHONE ME. I'm only licensed in CA. This answer doesn't make me your lawyer, and neither do follow-up comments and/or emails and/or phone calls, and you shouldn't expect me to respond to your further questions if you haven't hired me. We need an actual agreement confirmed in writing before any attorney-client relationship is formed. This answer doesn't constitute legal advice, and shouldn't be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue.