Grandfathered data plan, change phones
I currently have an iPhone with a grandfathered unlimited plan. Since the change at the start of 2016, will I be able to keep my current voice/data plan if
A) I buy a new iPhone through AT&T Next?
B) I buy a new non-iPhone through AT&T Next?
C) Buy any new smartphone not through AT&T and activate it on my existing grandfathered plan line?