Group Pricing Discount dropped when 3D secure bank check made

Hi,

I'm using ZC 1.5.8a and have one page checkout too. I have applied the Group Discount option with a 5% discount for some selected users and this works inside the cart as expected - the total reducing by 5% in the cart.

However, I've become aware (because customers have phoned to tell me) that when the transaction is referred to the customers bank for 3D secure the amount advised in the pop up box is the original gross amount. A percentage of customers are put off the purchase as a result.

It appears that the bank is being advised the gross amount not the net amount after discount. Can anyone with better knowledge of ZC coding advise where I can look to change the way Group Discount behaves so that the net discounted amount is checked at the bank. I do know that if a customer proceeds (often they don't notice the pop-up bank message is for larger amount!) the amount actually debited is the correct discounted one.

Any help gratefully received!

Thanks for reading this.