As a buyer you cannot delete a purchase once you have committed to buy.
You will have to ask the seller if they will cancel the transaction but you should be aware that they are not obliged to do so.
Once you commit to buy the seller pays fees so you should not commit to buy unless you are sure.
The seller does have the option to open an Unpaid Item case against you to recoup their fees....many prefer to do this rather than cancel the trnasaction.
