Insurance adjusters do not have a medical degree. They work with a very simple guideline on how the expenses are suppose to occur based on the profit and expenses.
It is very possible that MD think it is necessary but insurance does not agree. You can fight or just eat costs. Most time, most people just eat the cost and get over it.
You can fight but you have very little chance to win because I dont think anybody actually read the police in those small prints.
You can not refuse the payment. That will screw your credit to certain degree.