My Galaxy S9 does not receive updates
I have an AT&T branded Galaxy S9. Fully owned, no payments, not blacklisted. Using it on AT&T Prepaid's Unlimited Plan (the one without hotspot) since February 2019.
My phone's security patch level is March 1, 2019. My Android build number ends in SC7. Every time I check for updates, it says my software is up to date. According to AT&T's website, the "up to date" software for the Galaxy S9 is security patch level November 1, 2019 with a build number ending in SK6.
So far I have tried:
1. Checking for update through mobile data and through Wifi.
2. Clearing cache for the the update app.
3. Connecting to Samsung Smart Switch on my PC (it says my software is up to date (SC7))
4. Factory reset of the phone wiping all data, then checking for update.
5. Getting a replacement SIM card from an AT&T store.
Nothing has changed.
Any ideas why my phone seems singularly destined to not receive an update from AT&T?