https://wccftech.com/at-galaxy-s7-downgraded-to-quarterly-security-updates/

The Galaxy S8, S8+ and Note 8  started receiving their Android Pie in February this year, shortly after their successor’s rollout was complete. The global unlocked variants of the devices were the first to receive the update, and as usual, carrier-locked variants in the US took much longer. The update started rolling out to Sprint variants of the Galaxy S8/S8+ and Note 8 last week and today its the AT&T and T-Mobile variants are receiving it. The update for the Galaxy S8 series is available on both networks, while the Note 8 update is currently out only for the AT&T variant.

The OTA update weighs around 1.5 GB and includes the March security patch along with the usual Android Pie and OneUI goodies. Not all users might be able to download the update just yet, as it is usually rolled out in batches. To check if you’re at the receiving end of one, go to Settings, click on Software Update, and tap the Download updates manually option.