For compliance, once a user has been unsubscribed he'll be blocked from being sent. you won't be able to deliver any message to that user from any functionality under your account.

By going to https://admin.smsedge.io/blacklist-numbers/index will give you your optout callbacks.

Callback URL - http://edgepxl.com/postback.php?type=rm-fk&fk={{{dynamic}}}
​Description - In the offer URL (campaign/view/tester/offers) you can add a dynamic variable (for more information Integrating a Conversion Pixel) which you can callback to our system once an opt-out was triggered on your end.
​Example Callback - http://edgepxl.com/postback.php?type=rm-fk&fk=1557-1115-39824828272

Callback URL - http://edgepxl.com/postback.php?type=rm-u&user={{{YOUR_USER_ID}}}&number={{{PHONE_NUMBER_YOU'D_LIKE_TO_UNSUBSCRIBE}}}
​Description - You can subscribe any number from your account using the API call above. Note the number needs to be in international formatting (E.164 - https://en.wikipedia.org/wiki/E.164) without the plus sign. Example - 12127678347
​Example Callback - http://edgepxl.com/postback.php?type=rm-u&user=21&number=12127678347

For our non-technical clients, we can provide you with an optout link you can add at the end of your Text, then users can go to that URL to unsubscribe, once a user has entered his details he'll be automatically unsubscribed from your account. To get such a link please contact Customer Support.
Example Page: http://out15.me/