Buyers can't cancel orders themselves, they can only request the seller to cancel.
How did you ask the seller to cancel this order? Did you just message them, or submit a formal cancellation request through eBay, see: https://www.ebay.co.uk/help/buying/buyers-can-cancel-order/buyers-can-cancel-order?id=4004&from=EBAY...
If you didn't use the correct procedure it would be worth doing so now. eBay will forward it to the seller which should at least ensure that you get a reply. Please allow a few days for the seller to respond - it's only been two days since you bought it and it's too early to be sending them multiple emails. Things don't move that quickly on eBay!
Please remember that sales are binding on eBay and sellers don't have to agree to cancel orders. Most will do so, but some may refuse to accept cancellations.
If that happens, all you can do is wait until the latest estimated delivery date to see to see whether it arrives. If it doesn't, you can then use eBay's money back guarantee to claim a full refund. If it arrives but you still don't want it, check the seller's policy on returns, which you will find in the listing.
UK business sellers are required by law and by eBay to accept returns (although you would probably have to pay for the return postage), but private sellers and sellers in other countries don't have to. You can find more information on returning items here: https://www.ebay.co.uk/help/buying/returns-refunds/return-item-refund?id=4041
If you run into any problems feel free to ask again here. If you do, it would help to tell us the item number, and how you paid, as your rights may dpend upon this.
