If during the secondary verification process you select That's not my number or I never received a code, you will be directed to a "Help with secondary verification" page.
Here, you can select Send code to my number to retry delivery or select the Change my number option.
If you have a default mail client configured on your device, the Change my number option will auto-draft the beginning of an email to the sender so that you can request a number update. If no default mail client is configured, the Change my number option will be unresponsive and a manual message will need to be drafted.