You can ask a seller to cancel your item, but they do not have to accept.
In my humble opinion silly not to, as the buyer obviously doesn't want it and would send it back for a refund, so just delaying that time for the inevitable refund.
You may need to wait one day after the item's last estimated date for delivery, and if not received, and open a case for item not received, escalate on day 4 if not refunded before hand and eBay step in and force the refund.
You can leave appropriate feedback.
@ainewhelan