Amazon Tickets - Ed Sheeran

Hi
I tried to book Ed Sheeran tickets on Amazon website and whilst searching the site crashed during trying to choose tickets. After numerous attempts to log back in and failing I bought tickets elsewhere
Amazon have emailed me saying I have purchased tickets and have debited my account. They have charged me for tickets I didn't choose and do not want.
Amazon refuse to give me a refund as they can only do so if concert cancelled or rearranged. They used my debit card as payment which is not what I wanted to pay for the tickets with if i had been successful. It's not my fault their website crashed and they still charged me.
Can you advise what I could do now ? Thanks