I have a question. I purchased an S20 Ultra when it first came out from AT&T through a Next Plan. Well, I ended up paying off the phone, having AT&T unlock it so I can switch carriers. I now have a T-Mobile SIM in the device. Which company I'd responsible for pushing out my updates/upgrades such as Security Patches and Android version updates? Would like to know the answer to this because I know each carrier is different when it comes to dates of pushing out these updates.
You could do a Google search s20 ultra at&t android update then s20 ultra t-mobile android update and see which one matches to see if it's still with at&t. I would think it's on t-mobile patches now but that is a way to see.
It'll usually go by what your imei number was registered as on Samsung site, I used to be able to get around it by manually installing firmware of different carrier csc check your csc code see what it says it'll probably have orginal carrier then current carrier which may cause update issues like mine was xas/vzw/vzw
If you are using a t-mobile sim and on their network and using them as a provider then they will be responsible for your software updates. I'm a t-mobile customer and if you are using them as your provider then they will do them. If you are still using AT&T as a provider yet using a t-mobile sim and towers it's going to be a confusing process