I was wondering whether anyone could tell me how to configure so that Authorize.net knows the charges from my shop, which has the default currency set to GBP, are to be processed in GBP as opposed to USD. I am doing an event registration shop for a UK event, but the company collecting is in the US, so the account is set up in USD.

Under Modules > Payment I have the Authorize.net module installed (simple, not AIM), and under Localization > Currencies I have GBP as the default, value set to 1.0000.

The confirmation email that comes from the store indicate the correct price in and total in GBP, i.e. 450, but then the transaction receipt email I get from Authorize.net says 450 USD!!! How do I tell it it's GBP, not USD?

Please help!