A Florida mortgage broker has filed a complaint in federal court seeking a class-action lawsuit against Pontiac-based United Wholesale Mortgage Holdings Corp. and CEO Mat Ishbia over its March ultimatum that said the lender won't work with brokers who continue to do business with crosstown rival Rocket Companies Inc. and Wisconsin-based Fairway Independent Mortgage Corp. The complaint filed Friday by The Okavage Group LLC alleges millions of dollars in damages to the industry resulting from the March 15 deadline. UWM said brokers working with it and Rocket or Fairway had to sign an addendum agreeing to no longer originate mortgages through them or else pay a fine of $50,000 or more.