I'll never use Advanced Calling for the simple fact that it counts against your data plan. I'm on a very limited (2-gb per month) data plan, so I'm not looking to add to that if I don't have to.
Only video calls use data. Normal calls do not count against your data plan - they are counted as voice minutes, just as MMS messages do not count against your data plan - they count as messages.
See the FAQ: http://www.verizon.com/support/advanced-calling-faqs/
Open "How much does Advanced Calling 1.0 cost?"