I want to use Cortana on my Nokia Lumia 1520. To do so, the phone has to be set to English (USA), because Cortana is not implemented yet in Dutch. I removed my Dutch T-Mobile SIM-card, changed region to USA and Language to English(USA). I even uninstalled the Dutch language from the list. Fine, Cortana works!
But as soon as I place my SIM-card and reboot my phone, the region becomes The Netherlands and the language becomes Dutch and everything USA disappears. And Cortana refuses duty. I think it is a T-Mobile problem (Vodafone did work), but they know nothing.