A PBX (Private Branch Exchange) is a phone system that allows an organization to manage incoming and outgoing phone calls and also allows communication internally within the organization.
It provides features like transfers, voicemail, call recording, interactive voice menus (IVRs) and call queues and other useful features.

Here we can discuss how you can add a PBX Recording which you can use as an Audio File to be played for certain PBX features such as Announcements. 

From the Dashboard, click on Phone System and select PBX Recordings

 Under show recordings, click on Add Recording

Set up recording options.

• Description – The name of the recording.
• Select Audio File – Select the audio file that you want to play for this recording. To upload an audio file see FAQ How to Upload Audio Media
• Click on Add

At the lower right-hand corner, click on Apply Changes to save the settings.