Tango and Viber do not work smoothly on my Samsung Grand Quattro G=18552.The problem lies in that I as a caller or a receiver can hear and see the other person both in Viber and Tango,but the other person called or calling me is unable to either hear or see me.Request someone in the forum for help if any.Also would like to know whether if there is any sort of clash in Samsung held phones and Iphones.Don't know.