Help please read below , I’m trying to shipped

Product Details

Please help !! I’m trying to send my item that I sold it’s a backpack so I need a bigger box , they won’t accept it because is supposedly my box is too big they want me to buy a label for 13 pounds when this box weights only 4 lbs they want me to pay $50 I don’t get it ? , they said the bigges I can go with this label is 12 by 12 by 12 and this box is 18 by 16 by 7help please thanks I know they can do it I have received bigger boxes from here when I bought stuff

1. Your order is usually shipped out within 24-48 hours after your payment is received.
2. The tracking number of your parcel will be sent to you after your order is despatched. You may use the tracking number to check the status of your order online.
3. The shipping fee will be auto-added in the grand total when you send payment.

4.8