There are some tips here: https://www.webex.com/business-continuity/business-continuity-low-bandwidth.html
When I have an issue I:
close applications I don't need to have open (that includes attendees too!)
Plug into m router (sometimes it could be the wifi signal strength
Use the call me / call in option rather than computer for audio
Turn of video is video is not critical
If its more of a network issue, perhaps call Cisco Webex Support to inquire if if can somehow be tested
Hope this helps!!!
