​@banditoBurrito can you send more details on the response you get back along with any headers, body, and status codes? It sounds like the API failed to update the DNC. Did you check the DNC after calling the API?

​@Craig C. Yes I verified the number was on the DNC that we can view on the front end UI. Unfortunately i did not log the headers on my server but the response code was 200. 

We have started utilizing another API call to cancel the existing leads in conjunction with adding to the DNC and that has seemed to have fixed the problem. 

Okay, that should work, but it points to a different problem where lead lists are not working with updated DNC. I can ask the RingCX team to take a look as the API appears to work properly, adding your phone number to the DNC list.

​@banditoBurrito the DNC will only operate when the list is loaded and on a nightly basis. So the number will not be removed until one of those actions occurs. This is a function of the DNC list currently in RingCX.

​@Craig C. 
Thank you for the clarification!
So cancelling in conjunction is the correct solution.

And any re-import of that number during list loading should be caught by the DNC list. 

Correct! Overnight, there should also be a batch process run to remove DNC numbers from your lead lists as well.