When your Polycom SoundStation reboots, you may notice that your call history is empty. If you set a custom wallpaper then this will be removed as well. This is normal behavior for a Polycom and can't be changed by celito. You will find details taken from the Polycom User Guide below.
You may always view your call logs on the celito voice web portal at https://login.celitovoice.net.
The details above were taken from the Polycom SoundPoint Phone User Guide.