This isn't by any means a solution, but I've found I can reduce the annoyance of being on hold by hooking up my phone to a bluetooth speaker and then just going about my work like I normally would (sans listening to music) until I hear someone pick up. This might not work if you have other people around making noise, but it reduces the hassle a decent amount if you're alone or in a separate room.
I do similar but using wireless headphones, to get on with other tasks without being so affected, or affecting other people.
Even then, I find myself semi-paralysed by the anticipation. It's hard to focus on something else, in case I don't notice the pick up and then they hang up. A callback would be much better.
