How do I stop a Broadcast message from sending?
After you schedule your broadcast message, if you change your mind or need to make changes to it, simply go to the "Broadcasts" page. Then, click the "Scheduled" tab and click "Unschedule" next to your message.
Your message will be stopped from being sent, added back to the Drafts section, and you can edit it. Then, set it to be sent again with your new changes.