iPhone 6s from Vodafone will not activate on Verizon

[stewf]

I have tried asking Verizon and Apple both online and in person and no two people have given me a consistent answer, so I bring my quandary here:

I bought an iPhone 6s (model A1688) from a previous owner in Germany. It was originally purchased from Vodafone and (according to Vodafone themselves) should be unlocked. I have an account on Verizon and when I use my valid SIM card (it works in my iPhone 5) it does not stay connected to Verizon or activate. I took the phone to Verizon and they tried another SIM card but it didn't work. So I took the phone to Apple where it passed all hardware diagnostics. They even put in an AT&T SIM, connected right away, and made a test call.

So I know now that the device is fine and the SIM card is fine, but it still won't activate on Verizon. Verizon’s online tech support told me that they could not locate the IMEI or MEID in the "Device Management Database" so they could not activate it.

A senior support rep at Apple claimed this:

So there is a bit of misunderstanding through all of this which I think Verizon was trying to tell you but no in a more direct way. The iPhone that you have can “technically” work on a CDMA network, such as Verizon and Sprint. While also working on GSM networks, like AT&T and T-Mobile.

The issue lies in what they were saying it’s “Not in their system”. On a CDMA network, the iPhone’s MEID number has to be entered to activate properly. This MEID is built into the device, much like a SIM card you can’t remove. This leaves the field open to possibly not have a device be compatible at all on their network even though it has the hardware capability to do that. With a GSM network, you only need the IMEI and a SIM card.

Shouldn't any iPhone 6s work on any network? Why would it be restricted? Is there any way I can get Verizon to activate my phone? Do I really have to switch to AT&T to use this device?

Thanks for your help!