I am so sorry to hear this. It's not right but things never are in the insurance field. The only thing I can tell you is to keep copies of everything and names, dates, and times of the people at the hospital and ins co. you talk to. Depending on your ins co. you don't have to have a certain paper for an appeal. You just need all the facts and copies of everything!!! Copy and date them and even send them cert. mail so someone has to sign for it. Send that to them and it can take 30 days. And it really may not be the ins co, it could be that the hospital or Dr office failed to submit the doc's correctly. You need to know from the ins co what doc they are missing,if its a ICD code or did the hospital fail to pre auth, all these things can be done again with no problem. They just have to decide who made the mistake and correct it. Hospital billing offices are well aware of insurance related issues,you just keep them informed and let them know you are waiting on it. Since you were approved prior to surgery it is most likely paperwork that needs to be corrected. You have a one up since you have all the pre-approval doc's. DON'T LOSE THOSE, it's your word against them but if they pre-approved based on the hospital finishing some paperwork you need to know. Call the insurance company and talk directly to a claims mgr, don't take no, and don't talk to a sup, you want a mgr, sups can't do a lot. You want to know what the hospital failed to send in so YOU can get it corrected. Then you contact the hospital and same thing you talk to a mgr not billing, because it may be ICD codes that need corrected. These claims and pre-approvals go thru a lot of hands so anybody could have made the mistake but since the ins co approved it, they should eat it, if it should not have been approved. Hope this helps.