Duolingo-I want to request a refund

I done my free Duolingo trial and was told that I would get a 2 day warning before it runs out so I could cancel it and not pay for the year, but I never got my warning and today I was charge £59.99 for the full year. I thought they would only charge be around £12.99 for the week. But I have now cancelled my subscription and would like a refund for my money.