Prevent my locked AT&T Samsung S7 Edge (SM-G935A) from updating to Android 8.0

I am currently on Android 7.0 with my Samsung S7 Edge and would like to prevent the update to Android 8.0.

I contacted Samsung support and they first said it was not possible.  Another agent recommended that I go to developer options and turn automatic updates off.

Now my device has notified me that an update is available.  It will automatically update after so many notices even though I turned off automatic updates in developer options.

How do I prevent this update from going through?  I actually don't mind if this one goes through, but it will be the next one that is Android 8.  Turning off WiFi does not work either I found out.