Sorry to hear about your difficulties with this card.

I would start by politely asking for a delivery confirmation or tracking number for your card(s). If they don't have one, I'd politely ask them how an apparent delivery problem can be remedied on your end if they don't bother to include tracking information? It's a fair point, and it might make them inclined to be a bit more flexible about accommodating you.

If you bought the card with a credit card, you have the option to dispute the charge on the grounds that the "item was not received". This is an excellent reason to use a credit card if you're ordering something online or by phone.

If these options don't work, a quick contact to your local BBB would be in order. You could explain that they not only haven't shipped you the card, but they won't provide proof of delivery. It's possible that VisaBuxx would rather simply refund your money--especially if it's a small amount--than have to go back and forth with you further or suffer a negative report with the BBB.

Best of luck getting this resolved quickly.