I'm afraid a seller does not have to agree with a cancellation and you may well receive it, if you have paid. If you haven't paid , you will get a non payment strike after 4 days of non payment. If you gain another you will not be able to buy from most sellers on eBay, for a full 12 months.
Does the seller have a Returns Accepted policy? Then, on receipt of the item, you can return it, but you will have to pay for the return tracked postage.
@vi_564135