It is fairly common for the Section B insurer (i.e. your own insurer) to demand that you see their doctor. Unfortunately your insurance policy has a specific clause that allows your insurance company to send you to a doctor of their choice. Obviously the insurers have their ‘favourite’ doctors that they use over and over. The reality is that the sole purpose of your insurance company sending you to see their doctor is in the hope that they can cut you off from benefits and save themselves some money.
The best way to deal with this is to pay for your own treatment as long as you can and then submit the receipts to your own insurer. The longer that your insurer believes you are not getting treatment (and therefore not costing them money) the longer it will be before they want to send you to their doctor. Remember that in order for them to send you to their doctor, they have to notify you. Don’t make that easy for them. Make them “dot the ‘I’s and cross the ‘T’s” by making yourself unavailable for their phone calls and emails and force them to notify you by registered mail.