Contracts/Bills of Lading with freight companies

I work for a company in Washington State. We have a vendor in Oregon who we buy from once in awhile. My branch is unable to by direct, a sister branch can. When we do an order I have to make a Bill of Lading telling the freight company to ignore the Bill of Lading supplied by the vendor because they will ONLY SHIP to the sister branch not mine. Another freight company has told me that I can not do that because I am asking them to Violate a contract/Bill of Lading they sign with the vendor. Even though I make my own Bills of Lading they are no longer legally binding when they get a new one from the vendor that contradicts mine.