Small claims court, BBB, Yelp, Channel 7 news. Blow them up.

For real, call and email all the local news stations to help. They love stories like this.

This makes no sense. I've been working thru my grandmothers estate and every company refunded overpayments back to the estate.

ProTip - Always pay electronic transactions with a credit card when possible. Not a debit or direct transfer. This way if there is an issue you can dispute the charge and the card company will often reverse the charge or write it off. Debit card or real time transfer means the money is gone and has to be recovered which is 100x more difficult.