[header] How to block a number on att [title] Write down the number that you would like to block. [step] Make sure you have all 10 digits available before you arrange to block it. [substeps] At&t does not have the capability to block anonymous numbers from your phone. 
If the number you dislike is from " private number " or " anonymous " you should ask the person or telemarketer to remove you from their phone or list and never call you in the future. It is a good idea to enroll your number in the us " do not call " registry no matter what wireless service you use.