Once you click on Publish, the file is sent immediately to the DSP and cannot be stopped. You will not be billed if you do not serve impressions (activate the campaign) against the published audience in your DSP. If you published the audience on a schedule and need to cancel subsequent publishes, go to the audience in the Audience Library, click the 3 dot "action" menu to the right and then "View Details." In the Publication Information section, click on the down arrow to the left of the publication and click on Cancel Republish Schedule.