This company is totally out of line

actually, Ingenix is the company that United Healthcare works with for things such as fraud and subrogation.
In some states, it is mandated that auto insurance covers as primary. when a health plan covers as primary, but the auto should have, ingenix will work in conjunction to UHC to regain the funds that they spent during the time that auto coverage was not. You specifically do not have to pay the funds back, but the auto carrier should be working with Ingenix to return the funds for the services that they should have been covering. .