One of the topics " hot" today 's youth culture in Vietnam are using smartphones with services OTT ( over-the -top ) ( * ) comes . This can be said is a major achievement of the technology particularly attractive point of it is to help users enjoy the service free connection ( only need Internet ) . In the context of the Vietnam revolution " in unison corresponding " rate increases 3G , aspects of "free" it becomes a point of visual interest . For transmission service providers , especially providers of phone service , said it could be a nightmare . The simple reason is that when people can message ( text , sound and images ) and call each other for free , they will not need to send a message service or traditional telephone surcharge. So , not only in Vietnam but around the world are taking a tough battle between traditional network and supply companies OTT services . On a global scale , according to estimates by market research firm Ovum , the increase of the free messaging application that the network has lost $ 23 billion in revenue in 2012 , and is forecast this number will increase to 54 billion dollars in 2016.