To back up your old Viber calls, you can try the following steps:
1. Open Viber on your Windows device.
2. Go to the "More" tab.
3. Choose "Settings".
4. Select "Calls and Messages".
5. Tap on "Email message history".
6. Enter your email address and click "Send".
7. You will receive an email with a backup of your Viber calls and messages.
Note: If your old Viber calls are not shown in your Viber account, it may not be possible to back them up.
