MM-SUS, Invoicing and Vender Partner Functions

Hi Experts,

I'm confused about this new issue we're dealing with. We have a vendor "A" which has a PI partner function "B." Both vendors A & B are set up for SUS, with partner profiles, etc. When I create a PO with vendor A, however, and then create an invoice against the GR in SUS, the invoice created in ECC is against A, instead of B. Is there some way to address this?

I would have expected that ECC would look to the PO header (or maybe even the vendor master) to determine the appropriate partner.

Thanks,
Seth