Hey guys -- I found the thread from last year with a similar discussion. Although it was not exactly about avoiding the $30 upgrade fee, it was about getting an IUP new Verizon iPhone X/8/8+ to work on AT&T. The process is the same. As I said earlier, it worked last year but who knows if it will work now.
I hope what I posted is helpful
https://forums.macrumors.com/threads/activating-verizon-x-on-at-t.2082465/#post-25462577
I hope what I posted is helpful
https://forums.macrumors.com/threads/activating-verizon-x-on-at-t.2082465/#post-25462577