I have had a similar experience...
My surgery is Monday morning(Sept 19), I've had all my pre-op appointments with the surgeon and this morning I got my surgical hooks put on at the orthodontist. It wasn't until I left the ortho's office and called the insurance company (again!) that I finally got the good news that its been approved! Phew!
I have been on pins and needles for two months, and they kept me hanging til 5 days before I go in. So frustrating! I've spent so long psyching myself up for this major event in my life, while this week I just kept to trying to accept the chance of it not happening! Luckily, its all turning out as planned.
My insurance also asked for more information and records last week (Sept 7), which was weeks after they said they had all they needed. The last thing I heard was that they would give me an answer by the 24th! 4 days too late! The whole time I was wondering what I would do if a re-schedule was needed(un-do work arrangements, cancel family help plans, etc), or if they were just going to deny it altogether. I've had a million x-rays and records and work-ups made by the surgeons already, and even the office staff at the surgeon's were getting nervous.
Anyway, what I did was call them (insurance co) myself every single day since my Sept 7 appointment. I went by the belief that "the squeaky wheel gets the oil", especially since the doc's staff has been calling them everyday too. Eventually, I got through to people higher and higher up, until yesterday when I asked if they could expedite the response and somehow I got approval the next day. Whether or not that helped hurry it up, I'm not sure, but it didn't hurt. I still don't understand how they do things.
I would just call your insurance as many times as you can and ask for the status of your pre-certification. When they say it is still pending, ask what the estimated date of the decision is, then tell them you have been scheduled for the 21st and ask if they can expedite the decision to make that date. My best advice is to be as sweet and polite as you can possibly be because you'll always get more help! Then, call your surgeon's office and see if someone there can get the surgeon to call the insurance company himself. The last person I talked to told me that the people who decide these things will not talk to patients or anyone else, but will talk to the doctors.
I'm sorry you're going through this mess when your energy and focus should be on staying healthy and strong, not worrying about insurance! I was still in the same boat this morning. It sucks, but even if you have to reschedule, everything will be okay. I'm keeping my fingers crossed for you. Hang in there and good luck!!