[fpgeek]

It's not just just Verizon. AT&T, in particular, has a habit of locking important features (VoLTE, Wi-Fi Calling) to phones running AT&T-branded and certified software. So unless the device you want is sold by AT&T and you get the AT&T-branded version, you're SoL. They even do IMEI blocking, so even if your device could otherwise work...

[digi_owl]

I have the impression that Nokia had trouble getting into the US market because they refused to let US carriers modify phone firmware to disable features.

In particular when Nokia tried to introduce SIP support.