Hi.
As you have already placed the order on ebay, you do not have control to cancel the order from your end. However, I would suggest you please contact the seller first and insist him to cancel the particular order. if he is a good standered seller, He will definitely do the same else you can raise a claim against him to ebay or you can demote his seller account with a gift of negative feedback 🙂
so relax.
regards.
Sachin Jade.