Order paid, but cancelled, and refund takes forever!

I placed an order and used Greenbacks as a payment method. The next day I received an email stating that the order had been cancelled. I contacted Avo and they claim that the payment didn't go through, even though the transaction showed on my Greenbacks account when the order was placed. Now they won't refund me in Greenbacks and say I have to wait for up to a week for the Avo credits to be credited to my Avo account. The Avo agent also asked me for a screenshot of the Greenbacks transaction, which I tried to send via their pathetic chat interface, but apparently it never went through. Why can't Avo follow up the transaction that they initiated with Greenbacks themselves? Please get someone that actually cares to contact me and reinstate the order or process the refund ASAP.