Denied

Ok this is my first time posting. I have been working on my surgery for over a year now and now my insurance company calls me and says that it has a exclussion in my policy. That they will not pay for me to have this surgery, but told my doctor's office and sent me a letter as well that I need another 6 months with my dietician. I have called and they have called trying to find out why now that they are saying this when they never said it before. Well the question that I have to ask is this. Has anyone else came upon this problem and also I have heard that you can get help from other people to help you get this surgery. Any answers will help.. Thanks