Samsung's developers' team may not have Android 9.0 Pie planned for the Galaxy S7 and S7 edge seeing as they're more than 2 years old now, but there's still some software love for the two. The latest OTA that the company is pushing, delivers the September 2018 security patch and some stability improvements to the OS.
Te build number is G930FXXS3ERHD and it's been only spotted on the Galaxy S7 but will surely hit the S7 edge in the following days as well. And just like the Galaxy Note8 patch the other day, the September fix resolves 9 critical security issues and 18 that affect Samsung's software.
If you don't want to wait any longer, try searching for the update manually or use a VPN, that might help speed up the process.