Do you mean you can't find their payment details or they can't find their payment details?
What sort of dispute have they opened? If it is for item not received then you need to prove that the item was sent. You need to add the tracking details to the dispute.
If it is for not as described you should ask for photos of what they are complaining about and go from there.
If it is just a change of mind return it depends on your own Refund policy....do you accept change of mind returns?
