Changing Vendor to retrieve the book

I'm trying to open a purchased textbook on adobe digital edition and it asks me for the vendor ID. I purchased it with the Campus eBookstore vendor. But it doesn't allow to select that Vendor and have to have me enter the adobe ID. The thing is that I purchased the ebook through my college bookstore and I register with the campus ebookstore vendor instead of adobe id. When i try to reauthorize the book it only allows me to use the adobe id vendor (the button is locked and I can't select for other vendor) but not campus ebookstore vendor which I can’t retrieve the book now. I just wonder how can I change the vendor to campus ebookstore instead of adobe id?