Recovering voice mail can be difficult task. If you do not recover it before your current voice mail call session ends, the voice mail is deleted permanently. However, if your voice mail call session has not ended, you still have the option of recovering deleted voice mails. The exact method is slightly different based on your phone's carrier.
Press the "*" key after you realise you accidentally deleted a voice mail you need.
Press the "3" key.
Scroll through the list of deleted voice mails until you find the one you need.
Listen for the message "Check Erased Messages, Press 1, 9" while the call to voice mail is active.
Press the "1" and "9" keys as instructed by the message.
Find the voice mail you are looking for and replay it. Press "9" during or immediately after the message to save it and prevent it from being deleted again.
Write down your voice mail information promptly -- most cell phone providers automatically delete your voice mails 14 days after they arrive in your voice mailbox.
After you end the call sessions on Sprint and AT&T phones, deleted voice mails cannot be recovered. Deleted voice mails on Verizon Wireless phones cannot be recovered.