There are 4 different statuses for the Phonevite broadcasts:

• Scheduled - A Phonevite has been scheduled but has not started.
• In Progress - A Phonevite has started, calls are being made, but it has not completed.
• Finished - All calls for the Phonevite have been completed.
• Cancelled - A Phonevite that was Scheduled or was In Progress has been canceled.

Yes.

A scheduled Phonevite can be canceled at any time prior to the start of the broadcast. An "In Progress" Phonevite can also be canceled, but only calls that have not completed yet will be canceled.