Acknowledge the urgency
Say you will help get them back in.
Verify who they are
Ask for proof that fits your risk level, never just an email.
Explain the options
Offer backup codes, a recovery email or a manual reset.
Set expectations
Say how long verification takes and what you will need.
Restore access carefully
Reset only after verification, and log the change.
Advise on backup codes
Tell them to store new codes somewhere safe.