I did double check, but it was doing about 2GB a day at 2.4 GHz and about 3GB a day on 5GHz. Now it's maybe couple hundred MB a day. Perhaps it's a slow rollout.
To be honest, I haven't tried VoLTE on MB yet. Sounds like it's time to give it a whirl...
BTW. This is all in San Francisco.
All depends on the terrain/intended coverage area, sector alignment/tilt and antennas used.
Wide beam antennas in a 4-sector 90° configuration can actually do a lot of damage to the SNR. Alternatively narrow beam antennas at a 3-sector 120° can leave big coverage holes between sectors. It's a pretty interesting balancing act.