User B does not pick the call
User B - Missed Call (on the iPhone native call) iphone and Webex also shows notification.
User B sees the name of the user who tried to reach on iOS call history
User B - tries to call back
However, the call gets established via MRA/CUCM instead of the way the call was received(i.e. via Webex)
If there is a mechanism for Webex to understand what type of call was received from the missed call then it can initiate the call back appropriately. (Webex 1:1)