This is what BitPay says:
"As a payment processor, BitPay has no recourse or involvement in the fulfillment of a transaction. For this same reason fully paid invoices require explicit merchant approval to be refunded."
and
"We have already received several complaints regarding this merchant. Our compliance team has already restricted the account activity and is trying to negotiate resolution of outstanding purchaser compliants with the merchant."
They cant help you to get your money back, but if you need proof of payment e.g. for court then they can provide u with the url of your paid invoice.