There's two methods for removing (unsubscribing) subscribers from a campaign.
1) Customers can request to unsubscribe from your campaign by responding to any of your messages with any of the following word; STOP, END, CANCEL, UNSUBSCRIBE, or QUIT. Don't worry, we automatically unsubscribe customers that respond to your messages with any of these words.
2) You can manually unsubscribe a customer from a specific campaign by following the steps below.
Select the campaign the subscriber that you wish to remove is subscribed to by clicking the Manage button from your list of campaigns on the campaign dashboard.
Click the Subscribers icon in the campaign navigation bar in the top right hand corner of your campaign homescreen.
On the righthand side of the screen you'll find a search field, which you'll use to find the phone number you wish to unsubscribe.
Once you've found the phone number, click the View button for that specific subscriber.
Find the blue link that says Unsubscribe Now, and click it.
Confirm that they've been unsubscribed from your campaign by looking at the Subscriber State, which should be set to Unsubscribed after you follow the above steps.