Open a ticket and keep reminding FastTech that if they insist on charging you for postage after advertising all over the site and also the 'net that they are legally in the wrong.
If they say free shipping worldwide then that is what you should get.
Might also be worth contacting PayPal saying that FastTech are not giving post free as promised so are in breach of contract. If enough people bought then claimed money back PayPal would not be pleased.
Just keeping on at FastTech has worked for me in the past.
They try to wriggle out by claiming that carriers won't ship knives - not your problem, they state on the info page for the knife "worldwide free shipping" then they have to honour that.
On the other hand FastTech used to be my go-to site for knives, not any longer, there are better places to buy the best gear for knife buyers and collectors.