Booking issues

I tried to book tickets via their website. When it attempted to process the payment, it said that it can not process it at this point and that I must try again later. I looked and the seats that I was attempting to book were reserved. I tried on a different night, and the exact same thing happened. I waited on your phone line for 20 mins to try and clear it up, but I could not get through. I later received an sms from my bank saying that both had gone through. I would like then to cancel the second booking. I tried to register a complaint on their website, but I'm not sure if that worked as nothing changes on the page when your click submit.