I call and then start to deal with my other options. Since now you get that "callback" option you have a reasonable idea how long it will be to get a phone agent. And now that a headset is standard equipment for traveling it's a little easier too. However, it is true that sometimes the phone agents are frozen in the sense that they won't offer outside-the-box solutions to IRROPS, whereas airport agents will usually agree to any reasonable suggestion to get you where you're going if there are available seats.