I recently bought a 3.1 and have to say im quite disappointed. The handset is generic and the VoLTE and VoWiFi are not provisioned (I found this out by using *#*#4636#*#*) Contacted my network (Three) who do support both services, they could do nothing to force the phone to enable it so its obvious to me its a firmware glitch, reading the forum there are plenty of others with the same issue. Ive tried two other sims, same result.
Secondly, despite Android One issuing monthly security patches mine is still 3 months behind on September. Come on Nokia, sort it out, you used to be a good brand, what on earth happened?