In most cases, once a lottery ticket is purchased, it cannot be canceled or refunded. This applies to both physical and online tickets, as lottery rules generally state that all sales are final. However, some online platforms may allow cancellation within a short grace period before the draw, depending on their policies. It's important to review the specific terms and conditions of the lottery provider you're using to understand their rules on cancellations. If a mistake is made in ticket selection, you should contact customer support immediately to see if they can assist.