You can turn on partial caller IDs for users dialing into meetings by phone only. When this is enabled phone numbers for call-in users have the last four digits covered up with asterisks and look like this "Call-in User_1 (+1234567****)." This doesn't impact people joining from the Webex Web App.
1

Sign in to Webex Site Administration and go to Configuration > Common Site Settings > Options .

2

Check the Display Caller ID for dial-in users when available check box, and select Update .