iPhone, iPad and Facetime Calls

        Jim Hamm asks for information and insight.  He says, "A friend has posed the question whether using Facetime on an iPhone use cellular minutes or data from one's data plan if connected to wifi? From reading the comments on the Verizon Wireless Forum, some say yes and some say no. Apparently calls to Verizon get different answers. 

        Here is yet another set of conflicting comments on a mobile forum.
        "I did a bit more research on my iPhone 5 and in settings I turned off  'Data Cellular' wherein no data can be transmitted over the cellular network. I'm connected to wifi and initiated a phone call on Facetime and it went through fine, but I know it's not using any data from my data plan. However, It may still be using minutes from my cellular minutes plan even though I'm connected to wifi -- but I'm not sure of that. 
        "This  question is important for my friend in that she has a certain amount of minutes and cellular data and doesn't want to burn through that unwittingly. 
        "If an iPad is connected to wifi one can make a Facetime call and for sure no minutes or data cellular are used. But an iPhone is different in that a cellular plan normally is initiated in order to use the phone. Some carriers now permit a Facetime call over a cellular network (no wifi) and in that case for sure the call is using minutes and may be using the data plan as well since video is involved."
        Jim asks for input,  "If anyone has further insight into whether an iPhone connected to wifi uses cellular minutes when making a Facetime call, let me know if you would. Thanks."