What is advanced calling, and does it cost extra?
Advance Calling (VoLTE) is a feature that allows you to take advantage of HD video and voice calling. You must be on a monthly plan, prepaid does not include this feature. You must have a device that supports Advance Calling. There is no extra charge for this feature.
Advanced calling in and of itself does not cost extra. You CAN incur additional charges depending on how you use advanced calling, though. If you use the video calling aspect of advanced calling while on a cellular data connection, you COULD incur data overages to your monthly data allowance.
VoLTE does not count against your monthly data allowance. Video calling does count against your data allowance if done via cellular. Video calling via wifi does not count against your data allowance.