On Sunday, I booked a flight direct on an airline website and paid for all the fees. I received the email confirmation and a separate email for the e-ticket. I also managed my account online and selected my seats.

Today the airline sent me an email telling me that
"We regret having to confirm that due to a recent technical error in our system, we are unable to confirm your reservation with reference code ...."

I already have the ticket so I thought that the good is sold as you say if you buy the item in the shop. The airline is offering me 50% off on any base fare for the intended journey but I would still be worse off.

What leg do I stand on? Can I tell them no, they have sold it already and taken the payment from my card. I don't want to risk going to the airport and they cancelled my ticket!