i phone 5 wont link or sync to yahoo

just had to get a replacment iphone 5 after my 2 month old i phone 5 speakers stopped working, now i can get the yahoo mail to work keep getting server unavailable i have tried to use the other and yahoo setting under add accounts nothing works at all, i as starting to get feed up with the i phone 5 after dealing with all the data leaks and over data charges from that problem that was never fixed yet now the speakers and this whats going to happen next!!