So I've recently just bought a new S21 ultra from Korea. It's stated that it's unlocked, but when I start up the phone for the first time. I realized that it's running with a splash screen of SKT(Korean Telecom) and when I entered into the phone, I realized that I get this SKT services that I can't opt out for or change out for. And I realized when I put in my local sim card, it works, I can call and I can use the mobile data. But this is a 4G sim card I can only access LTE/3G. It's slow! Really bad. And I noticed that my sim card is registered as foreign on the phone. I'm not too sure what to do. Is there a way to unlock this? Is it unlocked? Or is there a way to activate 4G on my local network?
I can't seem to post links to the picture.