You can control which calling application is used and how calls are routed when people dial PSTN numbers or extensions from Cisco Webex. You configure this setting at the organization level, and you can also override your organization's default setting for specific users with different calling needs.
Before you begin
Your organization must have the correct subscriptions for the calling behavior you choose.
If you choose Cisco Jabber, make sure it's registered with the
Users must have valid phone numbers. If the numbers are invalid, Webex still sends the number to the calling app that you select, but the call fails.
From the customer view in https://admin.webex.com/, go to Management > Organization Settings, and then scroll to Calling Behavior.
Choose the app you want to use as your organization-level setting for calling within Webex and then click Save :
Users must have the corresponding application installed to make PSTN and extension calls from Webex. Make sure you let people know what choice you make and if another app is used to make calls.