If your phone number has changed and you have a new phone or the mobile device used for authentication is lost, you can disable multifactor authentication (MFA) via email so that you can register MFA for your new phone or log in to your LastPass account without the mobile device that you lost.

1. Log in to LastPass with your email address and master password from your desktop or another device.
2. Click Additional Multifactor Options.
3. When prompted, click the I've lost my <authenticator app name> device hyperlink on the bottom of the window.
   
4. When prompted, enter your email address, then click Send Email.
5. An email is sent containing a link that will allow you to disable multifactor authentication. Check your inbox, then click the link within the email.
   Note: If you do not receive an email, you may have a secondary security email enabled where the email was sent instead, and/or check your spam/junk email filters.
6. Once clicked, a confirmation window appears informing you that multifactor authentication for LastPass has been disabled for your authenticator.