Question about Samsung Galaxy J7 (2017) EU

Here is an excerpt from a 2013 AllaboutSamsung.co.uk article about this lock.

Statement on the regional SIM card lock before first use in current Samsung products
Some current Samsung products are now equipped with a regional SIM card lock. This means that initial activation for devices purchased in Germany can only be carried out with SIM cards from mobile network providers from Germany as well as from the European Union and the European Economic Area (the "Europe region") (detailed country listing on the following page). After the initial activation in the intended region, the use of SIM cards from foreign providers is still possible without restrictions. If a device purchased in Germany but not yet put into operation is activated abroad for the first time, users can have the SIM card of their device activated for the region free of charge at Samsung Service. Users of current Samsung devices can continue to use them together with their SIM card from a mobile phone provider from the Europe region via the roaming service for the corresponding roaming charges of their mobile phone provider all over the world.

Example to explain the regional sim card lock before first use:
If a user purchases a device in Germany and activates the device with a SIM card from a German mobile network provider, he can continue to use the device via roaming service against corresponding roaming charges of the mobile network provider all over the world. The use of SIM cards from foreign service providers is also possible without restriction after initial activation in the designated region.
- If a user purchases a device in Germany and wants to activate it for the first time outside Europe, the regional SIM card block applies. In this case, the customer can contact Samsung Service and request an unblocking of the SIM card block.