Looks like the same thing happened to me just now.
After finally receiving the backpack to the UK on which I paid 20% on checkout I now have to pay another £66 to parcelforce
Currently waiting for support to reply but I am assuming they have to refund the 20% charged,
Subtotal $322.96 USD
Shipping (14 - 28 Day Delivery) $79.98 USD
Tax (Standard Rate 20.0%) $80.60 USD
Total $483.54 USD