All of that app using internet protocol to work out.plus skype,SIP,jabber,fring or what ever.

for video call using 3G is work from our local service provider carrier is in different segment..so that why we discuss in this thread..majority of phone user or our contact mostly having this type of function on their phone.for some reason,it differ from telco service provider on each country which provide this service or not..
for my country and asia region this function is most popular for the past 7 year until now and we are still love using it because is cost going cheaper and sometimes provide special package on it..

not All of phone user is enabling their internet and login to their VOIP acc every time if they on mobile..so that why for some country,3G video calling it the most popular function and most reliable video calling for this time being because it based from our telco service provider and not depend on internet access..

maybe some of you can get idea from that..thanks..