Symptoms
Assume that you use a Microsoft Skype for Business mobile client to dial a Public Switched Telephone Network (PSTN) number in a Microsoft Skype for Business Server 2015 environment. When you view the Peer-to-Peer Session Detail Report, you find that the From number attribute is empty.
Cause
This issue occurs because the Microsoft Unified Communication Web API (UCWA) does not send TelNumber in P2PSessiondata.
Resolution
To fix this issue, install the December 2017 cumulative update 6.0.9319.510 for Skype for Business Server 2015, Front End server and Edge server.
