Even though you are in Luxembourg it should show a Spanish IP address, this is a very simple thing for you to do. I understand the point about unlimited data on your sim therefore you have no need to use wifi however you could have taken screenshot of what you see when you open the following website: whatismyipaddress.com
To address the Wifi point, I spend a lot of time at work where the Wifi is capped (cannot access many sites such as even youtube), therefore I always keep the Wifi setting off on my phone, given that I have unlimited mobile data anyways this has never been a problem for me.