You don't.
The eBay clerk was stupid.
The Global Shipping Program is meant as Seller Protection for US (and recently UK) sellers. Only they can opt in.
As a buyer you can't.
And probably don't want to. It is not a good fit for Canadian buyers or anyone making multiple purchases.
The first problem may be the shopping cart.
If you are buying just one item, look at the listing and find the listing number. It's usually on the right side in tiny numbers just above the description.
Put that into your Search box and go to the original listing.
Don't use the cart, just order and pay.
Are you buying from US-based and Canada-based sellers and trying to put all your purchases into one cart? Not possible.
Are you buying from several sellers?
This will be a little more time consuming but:
Go to each listing. If you have several items from one seller AND that seller is not using the GSP, just buy them, but do not pay yet.
Send the seller a Message asking for a combined and discounted shipping fee.
She is not required to agree, but most sellers will.
Pay for those items.
Go to the next item. Repeat if there are several items from one seller.
If not, just buy the item. Pay.
Repeat.
Now.
The bloody GSP.
Your seller can't combine shipping if her items are being shipped with the GSP. She just can't.
If your order is large enough, she might make a new separate listing for you (suggest using your eBay ID as the title) with all the items you want and a better shipping rate for them all.
But again, she doesn't have to agree.
I wish it were easier, and perhaps another of us old lags will have better suggestions.
