You are covered by eBay and Paypal's Buyer Protection policies.
For eBay go here:
http://pages.ebay.ca/help/policies/money-back-guarantee.html#description
You have only 45 days from purchase (not payment and not delivery) for this.
For PayPal
https://www.paypal.com/ca/cgi-bin/webscr?cmd=_choose-transaction&return_to=history
You have 180 days to Dispute.
The URL is not too useful, since you have to use your own account and I got that from mine.
Both will require you to return the item. You may or may not be required to pay for this.
You have 60 days to leave feedback. The most effective feedback is calm and factual.
'counterfeit not Samsung no response to complaint'
In addition you will be asked to leave the much more important Detailed Seller Ratings. A normal transaction gets 5 stars. The lowest Rating is ONE STAR. No stars is a free pass.
If the seller's DSRs drop below 4.3, his account will be restricted or even closed.