Hi @carolynd.eqm4zu and welcome to the Member Community.
See if this article helps.
Come on back if you have any questions
Has to be the U1 model. Factory unlocked…not a carrier unlocked model.
This post may be more informative.
One easy way to sometimes tell, is if, when u turn it on, and it boots up, is there a carrier logo screen, like Verizon or Tmobile etc…if so, it is a Carrier model, not factory unlocked (non-carrier) model.