I've just done this this morning to my samsung 850, the hack is as follows:_
Power on the player with no disc in the tray.
1.Press the repeat button your remote control
(don't confuse this with the repeat A-B button)
2. Press the buttons 5,3,8,1 and 4 on your remote control, in order one at a time.
3.The numbers 01 or similar current region code will be displayed on the top left of your onscreen display
4. Press the 1 button on your remote control for region 1,2 for region 2, and so on, or 9 for multiregion playback
NB: The above step may be time sensitive and need to be performed quickly
5. Open your Disc tray and leave open for 15 secs.
6. After 15 seconds have elapsed, power off your player and the disc tray will be closed and the player shut off.
7. Power on the player and it is now set to the new region code you chose in step 4 above.
Hope that helps!