A buyer can ask, but a seller doesn't have to cancel an order.
If the item was described for an adult, and a child's bangle arrives, open a return case stating Item Doesn't Match Description or Photos, the seller cannot refuse this.
If you have received an item not as described, go right of the item in your Purchase History and from More Actions select... Return this item selecting the reason Item Does Not Match Description or Photos.
The seller needs to accept this case within 3 days and refund, if they want their item back first , they need to pay for that fully tracked return postage, then on receipt of their item they have 48 hours to refund you. If they don't , need to escalate the case, ask eBay to step in, and they'll force the refund.
Never listen to any excuse or promise from the seller to close the case early, and do not forget to escalate.
@tsztg60
