Their mistake but no cash refund

I've always had good service from Hyperli, but now they refuse to refund my money. I bought a voucher which the merchant refused to honor, since their were conditions attached to the voucher that Hyperli did not disclose on their website. Instead of refunding the money to my bank account as I asked, they issued a voucher and refuse d to refund the money to my bank account. Shame on you Hyperli for penalizing me for your mistake!