Zend certified PHP/Magento developer

Magneto Base Currency set to AED but CCAvenue charges in USD

I have created a site with Base Currency as United Arab Emirates Dirham (AED).
One Website, one store only.
Default display currency is USD.

Catalog Price Scope is set to “Global”

CCAvenue is configured like so:

Screenshot of CCAvenue config

Question: Why does the CCAvenue choose USD as currency for billing? Here is the screenshot from the Sales Order :

Screenshot of Sales Order

Thanks for your help!