Zoom App Drops Calls for Multiple Users

Hello, I have an ongoing issue for users I support. Multiple users report their iOS Zoom App either drops calls, doesn't ring then shows a missed call, or when dialing out the call just ends. I have made sure to sign them out and back in, made sure cellular service is enabled for calls and same with WiFi, upgraded to the latest version of the app, and it doesn't seem to make a difference if they are in the office, at home, or using WiFi or cellular data. Any help would be greatly appreciated.