What do I do if someone asks me for a Google Voice verification code?

It’s likely an attempted identity theft and/or phishing attack – someone is trying to take over your Google Voice account or transfer your GV number to themselves in order to act like you and e.g. obtain access to your bank accounts. It’s bad.

Treat it as a crime – except not the one you could usually call police on – like others said – do not share any codes, block the person who is trying to obtain the code, be on the alert for any other attempts like this.