Hello. Need Help here!

I am using oscommerce shopping cart with default currency MYR (Ringgit
Malaysia) and my currency setting for my 2co account, USD.

When i select to pay via 2CO, my OSC cart send the amount in MYR currency without converting it to USD.

example:
Total payment = MYR 20.00 (my oscommerce cart)
Total payment = USD 20.00 (2co)

MYR to USD = x 3.57

that means, my customer will pay MYR 20.00 x 3.57

Can somebody help me, please?
How do i change the setting/parameters for the convertion?

Thanks