Taking there time to pay money back

I purchased a voucher through groupon on the 5th of August. The voucher was never issued. After trying countless times to get hold of them via phone, I eventually did so on the 7th. They asked me to proof to them that the money went off my account as nothing on the system reflects that I made the purchase. Speaking to Astrid, I kept trying to send the proof of payment. Eventually, on the 18th of August she responded that she received the proof of payment. Since then, NO communication. She ignores my mails requesting feedback on when the credit will be passed!