Wow that sounds really frustrating. There is no such thing as purchasing a W fare... it is a fare basis that books into W. So sounds like when your ticket was rebooked, an agent incorrectly assigned a new fare basis. Fortunately they should be able to see the history as you mentioned that one of the agents could. They have to look back into the previous ticket that was linked to the reissue to see the original basis codes, and those should be restored.

If you go to your ticket receipt and email it to yourself, I believe it will show the fare basis codes for your ticket so you can see what it actually is now instead of the Bxxxxxx