Which On-Call UI are you using (the classic On-Call Calendar or Service Operations Workspace), and which ServiceNow release? The Contact Sources configuration is for communication methods used by schedule notifications; it may not control the phone number shown in a schedule popup. First identify which user phone field the popup reads. If this is a privacy requirement, protect that field with an appropriate field-level ACL and test the impact for the affected roles, since that can hide the number in other places too. If you only want to hide it in this one popup, the supported option may depend on the UI/release. Reference: https://www.servicenow.com/docs/r/it-service-management/on-call-scheduling/config-contact-sources-on...
