Provider Directories

About a week and a half ago I received the following email (posted w/permission w/identity removed):

Hello Mr Gaba. Last year I had a BCBS insurance through marketplace and this year I switched to a Physicians Health Plan offering, also through the marketplace. I thought I had done due diligence. I was interested in switching to the University of Michigan system. As I shopped for plans the PHP website listed literally hundreds of potential pcp's near me in Ann Arbor. But as I began to try and sign up with a new doctor and called the number listed for each doc (usually the same U-M switchboard number) I found that none of the docs listed were, in fact, accepting new patients.

At the moment I cannot find a new pcp through my new health insurance. Is this legal? Have I any recourse? Where can I find info on what to do? They suggest that I try to get my former doctor to fill out a prior approval or out of network form...Hoping you can direct me to somewhere; thank you for any direction you can offer me.