Can't Merge Two BOX Accounts into One

Our organization uses our corporate addresses to login to our market agency's BOX. We enjoyed using theirs, and got our own. Now we are seeing that we are not allowed to use our corporate emails for our own box because they are already being used to login to our agency's box. What is the work around? It is not feasible to merge these two organizations accounts into one, as they are two completely separate businesses.