Payment Process Request created 2 payments and used 2 Payment Documents to pay invoices for a specif

Hi,

I paid 2 invoices via Payment Process Request for Supplier ABC.

1) Invoice Date: 07/08/2013

2) Invoice Date: 15/08/2013

The Payment Date was 15/08/2013

The Payment Process Request was confirmed and the system generated 2 Payment Documents. If I go to Payment Workbench I have 2 payments generated one for each Payment Document Number.

I was expecting the system 2 generate one single payment including the 2 invoices.

Which option of the setup shall I change (I suppose that in the Payment Process Profile) to achieve this?

Thanks,

cv