how do I block Unknown numbers?

Hi there! @RMHTC15 thanks for posting your question.

To get steps for blocking unknown calls on the make and model of your phone, please visit us at http://www.att.com/esupport/article.jsp?sid=KB102428&cv=820

Hope this helps!

Charise

Since you're in the Windows Phone forum - I assume that's what you're using.

To block unknown numbers within Windows Phone 8:

1. Go to "Settings" and scroll down to an option called "call+SMS filter".
2. Click it and accept the terms.
3. Press "advanced" at the bottom
4. Toggle "Block withheld numbers"