If this phone is like every other LTE phone that Verizon sells, and there is no reason to expect it not to be, it will be hard coded to reject every domestic (US) GSM carrier. There are a few of the Motorola phones that people have been able to get around this, but for the most part it won't work.
mtlguy, I'm perplexed with your issue. It's supposed to be unlocked so that you can use other SIM cards outside the US. It seems like some of the internal settings are stuck on Verizon. You have to figure out how to get into the manual programming menu and look at what the home NID & SID is.
Are you using the phone on a GSM or CDMA carrier? If it's GSM, all of that is supposed to be controlled by the SIM. This will be a problem for me next summer. I spent way too much money on international roaming this summer and I was planning to use a local SIM next year. Hell of a note, spend thousands on a trip and bitch about a $250 phone bill...