2 Samsung ATIV S GT-i8750 phones ...only 1 updated to WP8.1?

[Windows Central Question]

2 unlocked Samsung ATIV S GT-i8750 phones bought from the same online shop (the second 1 maybe 10 month later)...only the first one updated to WP8.1; the second one just don't want to update (same carrier)....????

OS version says: 8.0.10517.150
Firmware: 2424.13.10.1

...any ideas to convince this stubborn phone to update?

 

[xandros9]

Is 8.1 even released on that model? Because I'm not sure it was.
One could've been Preview for Developers'ed.