Can this be done? I've never thought to call when seeing a very badly needed flight come up as "unavailable" on the web. So I check and check and check and usually it comes through eventually after wasting a lot of time. So I can get on the "overbooked" list by calling? Is this true?

And if the above is true, can I check in at T-24 and get a confirmed boarding pass or am I restricted to airport check in only?

Thanks for this potential time saver.