Service centre with no staff answering the phones!

I finally booked tickets with Lufthansa yesterday after their website would not accept two different credit cards. I was promised that my e-tickets would arrive within hours but 28 hours later and nothing. I have called the service centre again and again and again but no-one ever answers. I have sent numerous e-mails but have had no responses to any of them! What is a paying customer supposed to do?