Yes never buy an Ergo from an unauthorised retailer. Amazon is tricky as well because the sellers all register the items under the same item code, fake or not, and they get stacked together in a warehouse and you don't know if you are getting the one from the legitimate seller, or the fakey one.
I spoke to a guy who had stopped selling them through Amazon because of this. His were genuine, but his customers were randomly getting real and fake ones because of the way the website operates.
Good luck OP, bank is your first port of call - they will probably tell you to wait about 10 days to see if anything arrives, then get a written statement from an authorised retailer to say it's fake, then they can claim the money back from the seller's account.
Mine took a while, and I did get it in the end, but I kept getting spam and also dodgy emails from the company urging me to pay them again via western union as their bank had taken away the money. 
Aww 
I ignored them mainly, after a couple of times where I just explained that I wouldn't be sending them any more money because they were selling fakes.
Talk to the bank on Monday and if you paid by debit card, and they say you can't claim, speak to someone else, because you definitely can, and not all of them know about it (or want to bother? maybe...)