[PHO?]

Can anyone help me please. I currently use Itunes for both my Itouch and Iphone. When adding songs to my itouch, I can simply drag and drop music. But when it comes to my Iphone it won't allow me to do so. It worked before i upgraded my iunes for both devices. But now when manually trying to drag and drop songs, it asks me to erase and sync songs. Is there a way to drag and drop without having to erase my previous songs? THANKS