I work at a well known health insurance company and have been there 6 years now.  My first two years I enrolled every employee we have for medical and dental benefits.  Did they tell you to send the letter to the benefit administrator or tell you the name of the person that is receiving this appeal?  Sometimes if you state you case pretty well changes can be made.  It might also help if you could get your endo to write a short letter or note explaining the importance of staying with an endo that knows your child history well.  This would show the importance of being able to switch plans.  At open enrollment time for medical benefits did they give you a packet or were you able to get the information and enroll on line?  When you are writing this appeal make sure you can prove that you were not aware of the changes with the PPO.  The best of luck to you,  I will also ask a friend of mine that is still in HR that works directly under our benefits administrator questions also for you!