Additionally consider hiring a professional patient advocate. They do charge a fee , but you might need the tenacity and experience they bring to the necessary negotiation  , especially if the amount involved is thousands of dollars.  You can check out the  National Association of Healthcare Advocacy consultants at www.nahac.com or go to find an advocacy   directory  online at https://umbrahealthadvocacy.com).  It is important to interview the advocate to understand the person’s credentials,  references, prior experience and especially their fees to determine whether it is worthwhile to proceed with them or whether you should mount the challenge on your own.