If you haven't even received payment from the 1st company then they don't have a leg to stand on. Let them spend the money to take you to court. Plus, most non compete clauses are normally written to keep you from working with the competition while you are working for them. After you leave, you have the right to work for who ever you please.
This is CABL.com posting #238836. Tiny Link: cabl.co/mbaim