In the call list of the Calls / Ongoing calls menu item, you see calls that should have been finished a long time ago (e.g. calls from last month or last year).
Recorded calls might get 'stuck' in the Ongoing calls list after an unexpected hardware/software event, if the recorder can not properly finish recording a phone call.
You can erase these calls using the Database Purging option in a Server \ Database menu.
Read more about database purging in our knowledge base.