User Activity

I bought an item from a seller and paid, they sent an enail saying sorry it's out of stock and that they don't know how to cancel it can I do it and obviously as the buyer I cannot. What do I do here? I paid an unexperienced person for an item, they ...
I bought something last night and paid for it but got an email this morning from the seller saying this "Oh I'm sorry I should have checked earlierIt is sold out so I have to cancel it. Because I'm the beginner I don't know how to cancel it and refun...