In now days after facbook whatsapp is the one of the best communication sytem.it can be downloaded free in andriod and ios and any other smartphone.whatsapp is devoloping so it can be used some of java phone.
Its iterfrence is so classy but not look so good like hike or messenger.it has a larger varity of stikers.you can share your pictures, videos instantly with your friends.whatsapp can be run on 2g network also.in the latest version of whatsapp they are trying to add videocalling on whatsapp.
So I realy recomended whatsapp.