When there are Multiple Servicing ALCs, How are GT & Cs linked to the Supplier Site records?

We have multiple Servicing ALCs and once the GT&C is selected, Can the users select the Supplier from the list of ALC values(Servicing) by the User on the Intragovermental Request Servicing Agency attributes, Oracle is defaulting the supplier to one of the Servicing ALC instead user should have the ability to select the ALC and create Intragovermental request and autocreate the IGT Order. Did anyone have this scenario? Please let us know, Can the GT & Cs not have any supplier associated and successfully interfaced into Purchasing and later to be able to associate from the Req? If there is