The seller requests a higher amount for delivery after the payment transaction

[logitan]

  Does a seller may after receiving the payment for the transaction, claim an amount greater than that shown for the delivery of an item?

[reallynicestamps]

No.

The buyer can suggest that if a faster or more secure method of shipping were used, that the buyer would be willing to pay for the enhanced service.

But the seller cannot charge more than he advertises without the buyer's agreement.