Ask the insurance company to email you your records and tell them which orders you want to dispute. Send them the receipts of the ones you bought. Then they will ask the pharmacy for some sort of proof that they delivered them to you which they will fail to reproducing probably. 

I think your claims will be believed more than those of the pharmacy as you have no incentive to lie about this. In fact the, you should be rewarded by the insurance company and compensated.