Did the original listing, available in your Purchase History, state "No additional import charges at delivery"? Some sellers still do not know that they are signed up for the GSP. It's possible your seller is one of those and that your purchase was sent directly from the seller to you, instead of being shipped to the GSP centre in Erlanger, Kentucky. Have a look at your receipt for the $36 additional charge. Who was the sender? Are these charges for customs clearance and taxes by the courier company?
Other posters here may know the next steps better than I do. If no one else responds to this post, try posting on the Buyer Central link on the Selling Discussion Boards - click on "Community" at the bottom of the eBay page. But here is my advice, for what it's worth:
Get all your documentation, the listing number, receipt for extra charges, etc., together, and call eBay. Ask for a GSP specialist. Do not try explaining this to anyone else. The CS reps do not even understand that there is an ebay.ca, never mind all the intricacies of the GSP. I have never had to try to claim money back under these circumstances, so I hope you get some additional advice here.
