Whatever you do, document everything! Every piece of paper you've sent them, everyone you've talked to on the telephone, everything that they'd told to do as next steps and your follow-up. Make sure you have notes on everything your doctor has done, and also everything your doctor's office may have sent into them.
Keep track of all of your paperwork and notes in a chronological file. If you have to fight your insurance company at some point, you want to have detailed notes of everything that has happened and when.