Glad you name dropped the app you use. Again, ask yourself why FREE? Not looking for small print and even if they do not sell your content, is it possible a company like Viber that has sister companies and many sponsors cross share the info for their benefit? We just see a hole in the FREE application concept and question How and Why.
Hola has related companies. Does Hola share information?
Hola does NOT share data. Hola does use private services to validate phone numbers, but, apart from that, Hola does NOT share.