Hi General,
Have you looked into a queueing system? Or a ring back system to save people having to sit pressing redial over and over again. If you could have a system on the phone that told you what position you were in the queue I think most people would rather have that. If they were too far back, they could decide to call later, but it would mean it when you got through wasn't down to chance.
Not sure there's technology that allows this but it might be worth looking into?
As it happens I was lucky, got through on about my 5th attempt, so no complaints from me really.
Do you know how many tickets are sold, presumably it's almost sold out already?