The APN is added, it's corect. With the same SIM (Vodafone Romania) and the same APN I have 4G on my Lumia 1520.

The LTE bands in which Vodafone Romania is working are somehow blocked by Verizon.

It's may be some way to unlock all the phone capabilities in order to use bands 3(1800) and 20(800)...

Any clues ?