Can i turn off the auto-source functionality that the Requisitions to Purchasing integration?

Summary:

I don't want requisitions created from smart forms or integration to have a BPA or CPA defaulted based on Supplier and Supplier Item Number if a BPA or CPA is not explicitly referenced on the requisition line. We have an issue where we have items on a contract that has preferred pricing that should not be available to all locations. When people order an item using the smart form or through an integrated requisition, and they reference the Supplier and Supplier Part Number, it is picking up the preferred pricing from the BPA. Is there a way to turn this