I discovered this immediately after being on two hours of tech support hold, but I'm definitely using it in the future:

LucyPhone

Basically, it waits on hold for you and calls you back when someone picks up. I don't know how it knows when someone has picked up, and I don't have a toll-free number (it won't dial non-toll-free numbers) for it to call for me to test it out. But I don't really care.