Express Scripts Automatically Billed Orders Without Approval Internet

I went to visit my doctor due to some nasty side effects of some medication I was using. During that conversation, the doctor had recommended an alternative, which I wasn't ready to try since there were similar side effects reported on those. He understood, but suggested he could call in a prescription if I changed my mind. My pharmacy on record, thanks to my health insurance benefits, was Express Scripts.

I later found that Express Scripts automatically shipped me the medication and charged me for the order. For a medication I have no intention of using. During animated calls with the CSR and his supervisor, I pointed out I did not ever give my doctor a "power of attorney" to make purchasing decisions for me. After all, I never had a chance to review the cost of the medication nor its side effects in detail to make a purchasing decision. The supervisor kept repeating that she "get where you're coming from, but we assume your doctor has discussed it with you." I pointed out that I don't care what their assumptions were, I didn't approve the order or delegate approval authority to my doctor.

How do I fight this? I've got the sealed envelop, but they have refused to accept it back. They tried to bill my HSA card, but they had an old card #, so that was rejected. But I want them to fix the issue, rather than have the persistent risk that they will label me "past due."