Samsung Galaxy S7 Active Updating Issue

I have a Samsung Galaxy S7 Active which is currently on Android version 7.0 and Baseband version G891AUCS2BRA7 (February 5, 2018 release).

As per https://www.att.com/devicehowto/tutorial.html#!/stepbystep/id/stepbystep_KM1136420?make=Samsung&model=SamsungG891A, the most current version is Android version 8.0 and Baseband version G891AUCS4CRK1 (November 30, 2018 release).

When I go to Settings>Software Update, it says "Current software is up to date."

I went into Recover Boot and did the Wipe/Clear Cache Partition, but this did not fix/change anything. 

For reference, I purchased the phone in the U.S. directly from an AT&T store, but I am currently living in Brazil. My AT&T cellphone account is frozen until I return to the States, so I only use the phone with wifi down here. I do have a U.S. VPN, and I have tried updating the phone with and without the VPN connected.

Any assistance would be greatly appreciated. Thank you.