also breaking data services
I've had reports recently that Samsung devices are now resetting APN settings when you change SIM, wiping anything you entered manually. That's a problem if your network doesn't have an entry in the default list: change SIM - lose data access, have a SIM glitch - lose data access. Manually entering the required APN seems to be beyond a surprising number of users, just check the giffgaff support forum for a daily reminder of this - or the 120k downloads of the app that does it for them.
Before that were reports that Samsung were blocking manual creation of new APNs, potentially locking out any new network and needing a work round for MVMOs like giffgaff on existing ones. (Sony actually did this first with the Tipo but it doesn't seem to have spread to the rest of their range)
There's a lot more SIM blocking monkey business going on at Samsung than region locking.