How to get lollipop update for AT&T version of Galaxy S5 when on different network?

[AC Question]

I bought my S5 when I was in the US about less than a year. To use phone back in India, I got it unlocked and using it on local network. When I look for a software update from settings, it checks for update from AT&T server. I want to know whether software updates when not on at&t network.