How do I stop my Samsung Galaxy S6 from updating daily?

Every morning when I turn on my phone, and sometimes during the day while it is still on, my phone says it wants to install an AT&T software update. I used to say yes, but have taken to telling it to remind me later because it is annoying and time consuming. But sometimes it just does it randomly during the day, and I cannot use my phone for 5 minutes or so while it updates everything. Why is AT&T updating their software so often? How do I stop this from happening?