(How to backup sony answering machine)
The Sony Xperia mobile phones include a built in but buggy Answering Machine.
On My C4 (E5333) the messages can be found in the protected folder /data/data/com.android.providers.contacts/app_voicemail-data
To be able to access these messages, you’ll need to root your device. I used “King Root” to do this since it can be done entirely from the phone, but your handset might differ.
To back up these files I just use “FolderSync Lite” from the Play Store. It supports root permissions. I sync these to my Google Drive. (I sync one way only.)
To play these files on Windows you need to rename them by adding the .amr extension. They seem to play OK in Media Player Classic or VLC Media Player.
A simple batch file can do this: ren *. *.amr
To Sync these messages to another handset, I use “DriveSync” although FolderSync Lite could have done it too. Then, on that handset I have an ES File Explorer shortcut widget to the Answering Machine folder, along with another “DriveSync Sync Now” widget. VLC Media Player on Android can play these files, even if you don’t add the extension.