Groupon refusing to pay back my money

I bought a groupon in September, 2 weeks after I bought the groupon I called them to confirm when I will receive my groupon. They informed me that they did not receive my payment in time (even though I made payment directly after purchase). They then told me I need to send them pop so they can pay back my money as the can't sent my item anymore, I had to go into the bank to get pop as groupon don't need pop for purchase. The bank gave me a statement where it shows the payment as they can't issue individual pop, I send this to groupon. After 3months I'm still waiting for my money they now REFUSE to pay me back..