Decline payment after approving it

I supp**** Discovery with all the relevant codes for a procedure and got preauthorization.<br> After the procedure they tell me that they won't pay for a certain code as there is something wrong on their system with the code.<br> They now expect me to pay for it after they had given me authorization in the first place saying they will pay for all the codes I provided.<br> I see this in the same light as ***** where they are trying to **** me out of my money by making false promises.