I'm planning on using the last part of my voucher on an international flight. I've booked several flights using my voucher, and it's hit or miss as far if the agent knows to waive the taxes. Is there something special I can tell them to make it clearer, and which taxes below should I not have to pay? Thanks in advance.

CARRIER-IMPOSED FEES
$140.00 USD
PASSENGER FACILITY CHARGE (UNITED STATES)
$4.50 USD
TRANSPORTATION TAX (UNITED STATES)
$37.20 USD
US APHIS USER FEE (UNITED STATES)
$3.96 USD
US CUSTOMS USER FEE (UNITED STATES)
$5.77 USD
US FEDERAL INSPECTION FEE (UNITED STATES)
$7.00 USD
US SECURITY FEE (UNITED STATES)
$5.60 USD
AIRPORT SERVICE CHARGE (ICELAND)
$16.10 USD
PASSENGER FEE (ICELAND)
$2.80 USD