Go to your order history and select the item. Discuss the issue with the seller and see possible solutions.

If you can't come to an amicable agreement after contacting the seller, simply raise a claim by opening a dispute within 15 days following the delivery of your order or the end of the package receipt confirmation period (as listed in your order details).

Most sellers will return your money in 15 days or less. 

Customs clearance/taxes are not included