It's AT&T Unlocked got it in April 2025
According to your screenshot, it's an S918U model. The U indicates it was originally a carrier-locked device. The phone wasn't properly unlocked by the original carrier and is running that carrier's firmware. You won't get any OTA updates unless you insert a SIM from that carrier. You can find out who that was by looking at settings > about phone > software information > service provider software version (see my screenshot).
Your other option is to take the phone to an authorized service center and have them flash unlocked firmware. There will be a fee for this service. See this link to find a service center near you:
https://www.samsung.com/us/support/service/locations/
Your other option is to take the phone to an authorized service center and have them flash unlocked firmware. There will be a fee for this service. See this link to find a service center near you:
https://www.samsung.com/us/support/service/locations/
