Activating iPhone6S in US that was purchased in Germany

[RebelSpirit]

iPhone 6s was purchased new by my company in Germany and trying to  activate in the US.  Everything works but phone calls.  Have tried restore function from Apple and three new Sim cards from Verizon.  When turning phone on Verizon shows in upper left and then goes to no service    Any ideas?

[vzw_customer_support]

RebelSpirit, we want you to have the best experience possible on our network. I apologize. Some unlocked devices will not work properly on our network since it was designed to work for another wireless provider. You can verify if a device is compatible on our network by clicking the link below: http://vz.to/1FGCRFC

LasinaH_VZW
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[RebelSpirit]

Went to the web link and ran through the the steps. It says Yes the device is Verizon compatible and the SIM won't check. Are there issues with US SIM cards in a phone that originated in Germany?