telecom area: customer and supplier at the same time.

hello,

as you may know, in the telecomunication area and especially for roaming, a customer may even be both vendor.

we got the list of supplier invoices (provider) but at the same time we charge the same suppliers as customers.

we want to treat in SAP-SD, for invoices is not a pb we can create them on SD as a bills (F2 type), but their bills should they also create SD as debit memo or treat them on MM?

thank you for providing your help.

thank you in advance.

Adil