There are one or two things you can do to prevent scams.
First, don't use Auctions.
Most Unpaid Item Disputes are over Auctions, which make up less than 15% of listings. And even most Auctions include a Buy It Now option.
Second, don't ever answer a buyer who wants to text you or who asks for your Paypal addess.
He plans to take your sale 'off-eBay' and send you a faked payment.
Third, bookmark you Paypal account and only check payments from there. It is possible for a buyer to mark a purchase as Paid, without actually paying (Because: cash on pickup). Fake emails "from Paypal" are also a running problem.
Fourth, as a buyer, back your PP account with a credit card.
Not only will your purchases go through immediately, but you have a third level of Protection on your purchases.
If you have to talk to someone at Customer Service, ask them if they understand that you are in Canada and we have a different currency, postal system and laws. If they sound confused, hang up and try again until someone does understand this.