One of the ideas is at the end of 1 minute on hold, send them to a special voicemail box. We announce we will call them back shortly but our phones are tied up.Have that Voicemail box send an e-mail directly to certain people or some other method to expedite the call back. I like when companies have a message while on hold that “You are #3 in the call queue. Continue to hold or press 1 to leave a voicemail and we will call you back.” Something like that.