We need to know how customer fees are evaluated

I manage to obtain my order yesterday after struggling to track my order, other thing is that I’m not happy the way Post Office handle the customer fees in terms of international purchases to be specific they don’t notify how they value the items, they just tell you the amount that you have to pay for customer fees and the amount is half of a price of the item that I purchased and I was not told why they are charging me this amount.#WIN When I ask one of the tellers he told me that he doesn’t know how the evaluations work so I think us as customers we deserve to know how post office evaluate orders.