There's two methods for removing (unsubscribing) subscribers from a list.
1) Customers can request to unsubscribe from your list 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 list by following the steps below.
Select the list the subscriber that you wish to remove is subscribed to by clicking the Manage button from your lists on the dashboard.
Click the Subscribers icon in the list navigation bar in the top right hand corner of your list 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 list by looking at the Subscriber State, which should be set to Unsubscribed after you follow the above steps.