When you open one of your campaigns you will have the option to edit all the details before actually sending it to your subscribers.
To edit an SMS Campaign:
Select the My SMS Campaigns option from the SMS Menu. This will open the Sent SMS Window.
You can edit draft campaigns by placing your mouse over the campaign title you want to edit and clicking on it. You can also click on the Actions button on the right-hand side and choose the Edit option. This will open the SMS Campaign Window.
For more information about working with SMS Campaigns, see the support topic How to Create a New SMS Campaign.