That's the question that's been asked by a few people, and as someone who didn't have a credit card until recently, I totally understand what you're going through. Unfortunately we're only selling tickets through Dramatix so my advice to you is.....*drumroll*
Get someone with a credit card to buy you a ticket and then pay them back. I'm sure you know -someone- with a credit card that would be happy to help. (I already know of several people who are doing this).
Your name doesn't have to be on the ticket, you just have to have the correct ticket code on the night, and since there's no booking fee you don't have to worry about your friend getting hit over the head with any hidden charges (by us at least, I'm not sure if there are any charges levied by the credit card company).
Alternatively this might be the time for you to sign up for a debit or credit card of your own (no advertising here, just a suggestion!)