Cristovao
I just got my refund on my credit card, and that was thanks to Darrell. I wouldn't waste my time with the call center anymore.
Since your Vox has already been shipped and by Purolator, you should try to get a Purolator tracking number and track the shipment all the way BACK to Kobo, and print out the result. At least you'll have a record that they have received the item back.
I've had other companies instantly refund my card even before they received back shipments I've returned, but I don't know what Kobo is like in that respect.
There's also this site where you can post as well, and it is monitored by Kobo staff.
http://getsatisfaction.com/kobo
If you do post there, they will advise you to write to the help link at Kobo and get a support ticket number, but at least then there is an official record in writing that something is being done. I think it's
help@kobobooks.com . Then you would post back to the getsatisfaction site with the ticket number and the Kobo staff there will work on it.