If you no longer wish to use your Google Voice number, it's easy to delete the number and have it removed from your account. Here's how to do that on the Voice website, as you can't use the mobile app for the task.
What to Know When Deleting a Google Voice Number
Once your number is deleted, you can't receive calls or text messages on the number. You can still view your call and message history, though.
After deleting a number, if that was the only number in your account, you have up to 90 days to reclaim that number if you want. Then the number is gone forever.
Remember that you can't delete your Google Voice number if you're a Voice for Google Workspace user.
Remove Your Google Voice Number
To start the number deletion process, launch a web browser on your device and access the Google Voice site. Sign in to your account on the site.
Once you're signed in, in the site's top-right corner, click "Settings" (a gear icon).
On the "Settings" page, in the left sidebar, click "Account."
In the "Account" section on the right, you will see your Google Voice number. Beneath the number you want to delete, click the "Delete" button.
In the "Delete" prompt that opens, click "Delete Number" to get rid of your selected number.
And your Google Voice number has now been successfully deleted. You're all set.
Want to get rid of all Google services? If so, consider deleting your Google account entirely.