Change my region ?

[Ja sam bratee]

Hi,
My friend is a long time player (since 2015) of OSM and he has a unique problem. His osm account is on his phone and he forgot the login info, we were wondering how to change his region without the need of loging out. The region im talking about isn't the one regarding the language of the game but the flag that's dislayed on the managers profile and in a league, like his nationality. He wants to change it from Croatian to Bosnian, he is Bosnian but lives near the border so he thinks the game might have assumed it wrong or he messed it up somehow.
Thank you and i hope you can resolve our little issue.