When I was fiddling with settings I seem to have accidentally charged a buyer postage when it clearly says free delivery. I spotted it before sending the item, and have messaged the buyer, asking him to cancel and reorder (or, if he wants, just cancel it). Is this the right thing to do, is there anything I can do to give a partial refund of the amount the buyer overpaid? Sorry about this, new to selling and all the delivery options are super-confusing. I don't want the buyer to lost anything due to my mistake.
