Yet another reconstructive surgery question

Hi every one good morning I am one year and 3 months out from WLS.  I have lost about 120 pounds and been stable for about 4 months.  I feel great, I have lost enough weight ( started as a light weight) and now I am pursuing some reconstuctive surgery.   In November my insurance company approved a lilatera mastoplexi(sp), but the employer was in the process of changiong insurance comapies and I did not get the surgery before the change.  Now the new insurance company says it is not medically ness.  How can one company deem that it is and one deem that it is not?  I am so disapointed.  Any way I am going to appeal of course but advice is needed.  What do I say in my appeal letter.  Will the information from the former company have any weight?   I have some money saved, I will try to have the surgery and get reimbursed if ness. thanks in advance for you help Madeline