Since Webex Calling only allows you to use numbers that are assigned to Webex Calling, the number has to be associated with a Location. Note that the toll-free number will have to be provided by your PSTN provider if you are using Cloud Connect, or owned by you if you are using a Local Gateway for PSTN.
Once assigned to a Location, you can assign it as the Caller ID to some Users in that Location. If the toll-free number is actually used for incoming calls to a Call Queue, then you will be able to use the Group Call Management features to select that toll-free number as the Caller ID when a call is placed by an Agent.
