After skipping the October patch, AT&T is now rolling out November update for Samsung Galaxy Note 9, Galaxy S9, S9 Plus, and S8 Active. Which bring November 2018 security patch along with bug fixes and feature improvements.
Galaxy Note 9: N960USQS1ARJA
Galaxy S9: G960USQS3ARI6
Galaxy S9 Plus: G965USQS3ARI6
Galaxy S8 Active: G892AUCU3BRJ2
If you are still waiting for this update on your device, you can check it manually by heading into Settings > Software Updates or you can simply wait for it.