Google has automatically linked Android users' phone numbers to every Google account signed into their devices without asking for permission. This means if you use personal, work, and separate accounts on the same Android phone, Google may have connected your number to all of them even if you kept them intentionally separate.
Android users have received confirmation emails from Google stating their phone numbers were verified. Google updated its support documentation about a year ago to make phone number verification opt-out by default. During this process, Google adds your phone number to all Google Accounts signed in on the device.
You can disable this feature by going to Settings, then Google or Google services and preferences, then All Services, then Privacy & Security, then Phone number verification. The exact path may differ by device. Check this toggle periodically to ensure it stays off.
Turning off the setting does not disconnect phone numbers already linked to accounts. To see which numbers are linked where, go to your Google Account Personal Info page. Select your profile picture in the upper-right corner, go through each signed-in account, open the Phone section, and delete any numbers you don't want associated with that account.
Scroll down to the Usage section on the Phone page to see which services use your number. Also review your Security and sign-in settings. If you added your phone number for two-step verification or to Google Pay, deleting it from the Phone page won't remove it from those services. You'll need to update those settings separately.