To stop a scheduled Campaign, click on Campaigns on the upper menu. By default you will see all Campaigns you have created.
Click on Scheduled on the left hand menu to refine the list by only scheduled campaigns.
To stop your scheduled campaign, click on the Actions drop down menu and select Revert to Draft. A pop-up will appear asking you to confirm the cancellation. Click OK to cancel, or Cancel if you have made an error.
If you wish to delete your campaign, you must revert it to draft first. Then you can click the the drop down menu again to choose Delete.
Please be aware that BOMA will let you edit or stop a scheduled campaign up until 20 minutes before the campaign is due to be sent. In that 20 minutes you will no longer be able to edit or stop the campaign as the content will be locked for sending.