some years back, every Singapore citizen who was traveling abroad had no other app to use in calling back home apart from Skype. So, Skype was compulsory, as it was the only means of calling their parents, relatives, and friends back home without paying huge phone bills.
The difference between Wi-Fi calling and Wi-Fi offload is hard to tell. Even some telecommunication experts fail to differentiate them. People are always talking about these two kinds of technology. Although they are often connected. But whatever defines and separates them is not distinct.