When a user posts an ad not may indicate the price of shipping charges, ie, when a user purchases a product and pays your purchase, shipping costs are always 0 and buyers do not know exactly the price they have to pay if they buy the products.

Shipping charges vary by product sold but you can not specify the amount to add to the cost of the final payment.

I mean that users can not indicate in advertisements the item price and the price of the shipping separately. And then at the time of payment, shipping charges will be added to the final bill.