How Google Voice works
Google Voice stores, processes and maintains your call history (including calling party phone number, called party phone number, date, time and duration of call), voicemail greeting(s), voicemail messages, Short Message Service (SMS) messages, recorded conversations and other data related to your account in order to provide the service to you.
You may delete your call history, voicemail greeting(s), voicemail messages (both audio and/or transcriptions), Short Message Service (SMS) messages and recorded conversations through your Google Voice account, although your call history for billable calls may remain visible on your account. Some information may be retained on our active servers temporarily for billing or other business purposes, and residual copies may remain in our backup systems. Anonymised copies of call record information, with no personally identifiable information, will be retained in our systems to meet our reporting and auditing requirements.