OK, so the issue is unpaid customs fees, which you can pay the courier to sort out for you. I thought they were demanding extra postage or something like that.
Say you order an USB-to-centronics adapter from China. Then the DHL/whatever courier brings it to you and says "you have to pay €1.07 VAT on that, and also a €25 handling charge to DHL for acting as a middleman between you and the customs office". That €25 stings.