Due to a recent backend system update, some players have received a Name Change notification despite having an appropriate Riot ID. If this happened to you, check Changing Your Riot ID to see what you can do (like keeping your game name!) and can't do (like using the original server tagline, eg. NA1, EUW1, etc). And sorry for the inconvenience—some decade-old systems just won't modernize without a fight.
Unexpected Name Change
Wolf