ups keep charging me extra on USA postage a week after booking!!

chillies1

I use UPS website to send 46cmx31cmx31cm 8-8kilo packages to the usa via there mutli parcel deal a couple of times a week. I pay direct by paypal but a week later they take an extra unexplained charge from my paypal account, about 15-20% on every shipment. the original quoted charges  already include Peak and Demand Surcharge and Additional Option Fees Declared Value. Anyone else having this problem? I have complained but no direct answer regards why. I did get one saying they will send credit note a month ago but nothing happens, and I constantly have to chase up every order. any ideas on how to get round this ? it is a shame as they are the cheapest way to send multi parcels. thanks

sheramber

Is the payment for customs duty?