Emergency Dental Care USA

This dentist overcharged me by over $500 in January. They have stopped returning my phone calls and emails.
This emergency dentist overcharged me by over $500 in January. They claimed I was on a list for that money to be sent back to me. I've emailed and called and now no one will return my call, email or money. My HSA card is now suspended because I don't have over $500 to pay back - since the IRS requires proof of services rendered. It's now May and I'm still without the refund of overpayment and cannot use my HSA card. Which means I can't get dental work done at my dentist.