If you still want / need it. Pay the guys, they sent it, it is not their fault it got tied up in customs (

customs
btw, messed up a few of my shipment dates).
If you don't return to sender, anything else I'd say is tantamount to theft. You payed, were refunded your money & therefore should refund the product or pay for it.
Read the rest of the thread, refusing to pay & refusing to send back? You're definitely on my blacklist.