Pharmacy sent unordered drug - how to make them stop billing me?

When mother entered memory care almost 8 years ago, we had to use one pharmacy for the pill packs. We had various problems with them over the years, but I'd call and they would fix it.

When she came off hospice in '17, we kept that pharmacy and used a house call service at the MC since ours does not have a doctor. They do have (Zoloft) on the medical record.

In Sept, she went back on hospice. Hospice uses a different pill packs provider now. The nurse says she told the original pharmacy to discontinue meds, but an order for vit d wafers came in from the Dr service *after* hospice admissions. I tried calling to stop it and was assured, but I'm not a med professional so they ignored me. Hospice nurse called but has no record of calling, and they eventually stopped the vit d 2 mos later.

There was another drug, this sertraline, which I assumed was the only thing she was on from hospice since I did not know hospice used a different pharmacy now. It was not until we had the vit d stopped that I realized I was being billed for this drug. I called several times to no avail, and finally hospice sent a written order in Jan to discontinue all drugs from this pharmacy (I have a copy of the DC order). I received a bill for the drugs sent in Nov in Dec, and sent a letter to the pharmacy pointing out that it was never prescribed and demanding the total of $77 for the drug while on hospice be refunded and cited the fair credit billing act of 1977. I sent this certified, return receipt. No answer has come.With Fair Credit Act, apparently the amount has to be over $50.

The state pharmacy board says they can do nothing about billing errors, but if I have evidence the drug was sent without a prescription, they will look into it. I just received a bill for a monthly fee that appears to run if you have a balance.

What's my next step? This is not about the money, but about the sloppy record keeping.

Edited with additional info.