A1549 iPhone 6 and VoLTE

In order to not lose voice, I have upgraded my iPhone from a 5c to an iPhone 6. The nano SIM was moved over, and appears to working correctly, other than for one detail ... SMS and voice is still trying to use 3G. The phone was setup by creating a 5c backup to iTunes, and then restoring it to the iPhone 6.

My carrier is h2o (an AT&T MVNO). When I check my phone at h2o, it says that I'm good to go for the AT&T 3G shutdown (which means that the IMEI is telling them I have an iPhone 6). But the option in Settings > Cellular > Cellular Data Options to enable 'Voice & Data' is missing.

Is this a situation where the carrier needs to send a new profile ?