My wife will get told one thing by the doctor and another thing by the insurance company and she has to be the middleman to try and get the two sides to play nice and work with each other. You have to document things very carefully and it is a very long and painful process. If you can find someone in either side that is customer service oriented and is a problem solver, it helps immensely.
In the end, both sides just hope that you will get tired of the extra work and pay the money.