Simple Delivery only approximates the weight, so it's supposed to be OK if the item weighs more than it says on the label. However parcels are still refused so it's usually better to cancel/refund the transactions with the buyer's agreement (via the dropdown menu arrow for the item on your orders list) and relist with correct postage for the buyer to buy and pay again. Either combine on one listing with correct postage, or list separately and ask buyer to buy separately.
