Currency used in the cart must match the currency of the seller account

My client's Google Checkout account is based in UK, hence its default currency is GBP. Accordingly, I thought I'd let users pay using GBP - they actually think they are paying in USD but behind the scenes I convert USD to GBP according to the conversion rate.

Anyway, I keep getting the following error message:

The currency used in the cart must match the currency of the seller account. You supplied a cart with USD and the seller account is associated with GBP.

When I check the Integration Console for the message that is being sent from the website to Google Checkout's API, this is what I get:

_type=checkout-shopping-cart&shopping-cart.items.item-开发者_Python百科1.item-name=Credits&shopping-cart.items.item-1.item-description=Description&shopping-cart.items.item-1.item-currency=GBP&shopping-cart.items.item-1.unit-price=64.42&shopping-cart.items.item-1.quantity=1

As you can see, I made sure the currency is set to GBP, yet it still complains. Is there anything I can do to fix this?

How are users thinking they are paying in USD? If they see the Place Order page in USD, then the cart is posted in USD, hence your problem.

Also please keep in mind that credit card companies will add extra fees for currency conversions, which are unknown at the time of transaction to both the seller and Google Checkout. Usually the fees appear as a separate item on the buyer's credit card statement. You may want to inform non-UK buyers about this and emphasize that the currency fees are out of your control.

This doc has some info related to this error:

https://checkout.google.com/support/sell/bin/answer.py?hl=en&answer=71444