If you want something that always works,
1-Install "iFile" or ssh to your device,
2-then go to "/var/mobile/Library/Preferences" on your device,
3-(Make Sure To Show Hidden Files) if using "iFile",
4-open ".GlobalPreferences.plist" with a text editor or Property List Viewer.
5-go all the way down to "AppleLocale",
6-change the "<string>ar_LB</string>" or whatever is there to "<string>en_LB</string>",
7-save and exit,
8-respring or reboot.
if you backup your device and later on restore this backup to any phone without jailbreak it will still be there, just make sure you don't change the localization by mistake coz you have to do this again.
Good Luck
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