Over the past couple of years, Samsung has introduced region-locking to some of its unlocked handsets — particularly in markets like Europe and Latin America. The idea is you wouldn't be able to pick up a new Galaxy phone in one region and immediately use it with a SIM card from somewhere else. (This is not to be confused with network-locking, where a phone bought through a carrier is locked to its network.)
The same applies to the Samsung Galaxy S7 and S7 edge — models SM-G930F and SM-G935F, if you're keeping track — which have just officially launched across Europe. Pick up an unlocked GS7 or GS7 edge and its box will be sealed with a sticker reading "European SIM card only."
The tab below this sticker explains how and why, albeit in tiny and rather verbose script. Essentially, in order for your unlocked European GS7 to be fully unlocked, you first need to make a total of five minutes worth of phone calls using a European SIM. If you don't do this, and try to use it with a SIM from outside of Europe, it won't connect to the network.
Even without this requirement though, you can still use your brand new Euro GS7 on any European network you like.
Samsung's trying to scupper grey importers, not regular consumers.
So why is Samsung doing this? It's most likely intended to scupper grey importers — sellers who offer European Samsung phones for sale in regions they're not intended for. (And that's an increasingly attractive proposition given that Samsung's still not selling unlocked Galaxy S7s in the U.S.) The region lock lets most regular buyers have a completely unlocked phone for use around the world, after first using it for a short while in their home territory, while roadblocking anyone who's bulk-shipping Euro GS7s to other parts of the world.
It's a minor inconvenience, and something we'd rather not have to deal with when we're paying top dollar for a brand new device. But at the same time, a five-minute phone call (or five one-minute phone calls, or whatever) is a fairly small compromise.