on 03-03-2018 06:00 PM
If it is only in your cart and you have not purchased, you can just hit the delete button (it says something like 'remove from cart') when you click on the cart icon, I don't remember the exact wording now as it has been a long time since I used the cart
It is unlikely you have bought anything because you say you hit a wrong button and buying is not a one button process
*IF* you have indeed bought, you need to message the buyer and ask if they are willing to cancel, but be aware a buyer is not obligated to do so as they are charged fees as soon as something 'sells'