Anyone familiar with ccbill?? I really need some help!!

Simple as this:
I have a shopping cart on a website, selling downloads. customers can buy any amout of items, any combination of items, and receive discounts for purchasing a set amount of items.

So it's just a really simple and clear shopping cart system. And yet it is a problem!

So if I appear a bit silly or stupid, please help me here!!! I cannot figure out how to make this kind of shopping work with ccbill's checkout page and billing system, the accounts and subaccounts stuff. To me it seems I can only send one item at a time to ccbill checkout and I also haven't found any way of giving a discount for this kind of purchase.

I've found some information about upsales and loyalty discounts, but they don't seem to be exactly what I need.

I think I'll have to forward this message to ccbill as well. I have asked them twice already and they have not really given me a clear answer on this. If you can, please help me on this!! Greatly appreciated!!!

If you know ccbill and cannot see any problem here, please let me know!!
If you can see a problem that you know cannot be solved, let me know as well!!!

Cheers.