Unfortunately if the PO was already sent to the Supplier through the AN, I do not think there is a way or resending it to another Supplier. The only option I can think of right now is Printing the PO in P2P (Print as PDF maybe) and send it via Email to your Supplier.
If you then change your supplier data to reflect the changes (modify the networkID in the Supplier files), the future POs should be delivered to the correct Supplier on the AN.
The other option - which is probably not ideal - is to cancel your PO, modify your supplier data to reflect the new AN ID and recreate the PO same.
Now I also remember that there used to be an option to link Supplier accounts on the AN (example, 2 supplier accounts were created by mistake but only 1 of them should be used), but I am not sure if this option is available in this case and how it really works. Maybe someone from the Supplier Enablement Teams could jump in and advise on that.
Hope this helps.
Thank you, Lucie! We decided to cancel the PO and regroup. Supplier merged with another supplier and we need to simply set up the new supplier in our own system. So I'm learning a lot lately about supplier information management in several systems (not just Ariba!).
No problem Holly. Do not hesitate if you have any more questions. I'd be happy to help