Hi, I was lucky enough to grap 3month Stadia Code from r/Stadia
However, I was signing as fast as humanly possible which led me to a name of JOE lol
I been trying to find Support Chat, or email Support to Request name change.
Keeps linking me circles, cant find my way round.
You'll need to use the contact feature to find an active method to contact support.
https://support.google.com/stadia/contactflow?hl=en-GB
Chat and telephone support are not always available 24/7 and less so recently with the pandemic. So you may need to check multiple times during the day to find an option that suits you.