I forgot about this. Old Samsung phones (older than S7) had specific firmware for each carrier model and there was no universal or unlocked firmware for the US variants so you're stuck with the carrier branded firmware of whatever variant you got, Verizon in your case. One of the less desirable models to be stuck with, right after the Sprint model (SM-N910P).
A bunch of ServiceMode codes are disabled on Verizon, Sprint and AT&T firmware and no easy way to get around unless you root the phone, which was a bit complicated on every variant except SM-N910T because they all had permanently locked bootloaders.
NetMonster app might work since the phone is Snapdragon based, you could try that as an easy alternative.
Mobile network monitoring app
play.google.com