Yan, You have to try and understand what you are specifying when you add your attributes.This code works, because number 1 it knows that 'New' and 'Old' variable types are string where what you had would have just produced an error. This ArrayCollection that you are creating is just a collection of objects so it works as attributes for the graphic.private function addsymbol():void{
var myGraphic:Graphic=new Graphic(new MapPoint(100,50));
myGraphic.symbol=infoSymbol;
var attribs:ArrayCollection=new ArrayCollection([{myphone: "123",AGE: "New", VALUE: 23},{myphone: "2345",AGE: "Old", VALUE: 78}]);
myGraphic.attributes=attribs;
myGraphicsLayer.add(myGraphic);
}