Do you remember how region locking worked on the Samsung Galaxy Note 3? Basically, if you bought an unlocked Note 3 in Europe and brought it to America without activating it with an European SIM first, you were in for an unpleasant surprise. To be able to use it, first you had to make a call with a SIM-card by a carrier from the region where you bought it from - Europe, America, Asia, etc. Still, Samsung's support or an online unlocking service would have taken the chains off for you, so it wasn't that big of a crisis. But Samsung should have been more open about the region locking from the beginning.
Unfortunately, Sammy decided to go the extra mile to ensure that importers would have a harder time with unlocking Galaxy S Fives before selling them off. Alas, regular users are at a disadvantage, too. What's going on? Well, to activate your S5 that you bought from Europe, for example, you will not only have to pop in an Euro-SIM, but actually talk for five minutes with it, which means you need a pre-paid, or otherwise working subscription. Congratulations!
Still, Samsung is open about the precautions this time. Special stickers found on European Galaxy S5 boxes suggest that the user must make cumulative calls over five minutes in length with a SIM card from an European operator. Fair enough.
What should you do? Well, it might be in your best interest to avoid buying a device locked out of your region in the first place. But if you absolutely have to, then you can ask Samsung Support to unlock your phone, or use a specialized region unlocking service. Perhaps the developer community will think of other ways to "jailbreak" the smartphone, but alas, these things don't happen overnight. Either way, enjoy your Galaxy S5.