Incomplete refund for an order THEY MESSED UP

They never completed my order. When I complained they simply asked for proof of payment, which I sent them. They then sent an email with a partial refund. Not even an apology or an explanation. I paid with a voucher and then an ETF. I would like the cash back as I paid it in and then a voucher. Sloppy and unprofessional and again, not even an apology for time wasted.