Google will soon roll out changes to Voice intended to prevent unauthorized access to our voicemail inboxes. To access accounts via phone, you will now have to call from a verified forwarding number. If you're calling from a number Google doesn't recognize, you will be prompted to enter a verified number instead. In addition to this, PIN codes can now be up to 10 digits long. These changes will take effect starting on the first day of October, and anyone who signs in via a web browser should receive a notification giving them a head's up.

If you want to tinker with your phone forwarding or voicemail settings before these changes take effect, here are instructions for doing so straight from Google.

Source: Google