@Hodgson
If you have a Nest Account that you have NOT migrated to a Google Account, there are instructions here for updating your phone number:
https://support.google.com/googlenest/answer/9295081
Note that it says:
"If you plan to get a new phone number and stop using your old one, you should turn off 2-step verification before you deactivate your old line. Then you can turn 2- step notification back on with your new number.
Important: You’ll need to enter a verification code from your old phone number one last time. This is a security precaution to confirm your identity and help protect your account."
Due to security restrictions, I'm not sure if Google Nest Support can help you if you are using 2-factor authentication and have ALREADY changed your phone number, but you could try:
1. Go to https://support.google.com/googlenest/gethelp.
2. Select a category/product family, and type in a brief description of the issue, then click "Next".
3. Click "Other", then click "Next step".
4. Under "Resources", just click "Next step". (Clicking one of the listed links will bring up a Help page page.)
5. Under "Contact options", choose to get a phone call or chat with the team, depending on availability in your country.
If you have a Google Account, there are instructions here for updating your phone number:
https://support.google.com/accounts/answer/3463280
