Att branded volte?

I've spent the last few days trying to get a correct answer on this. The pages I've read say unbranded nexus 6 doesn't get volte on att. The phone I'm using was purchased through att with att boot screen and logo on the back. Wouldn't this make it a branded phone? My att lg g4 had volte, first I just put the sim card in the nexus hoping to keep the feature, but it didn't work. Today I updated them with my nexus imei and still doesn't work.

Does no version of the nexus 6 get volte on att?
Thanks

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