Called UA today to confirm which fare base codes could be used on LH when using a paper SWU. I have used one in the past but could not remember which codes were valid. Anyway, explained to the 1K agent that I wanted the fares that could be used. She told me that only B and Y were valid or I could buy up with miles and cash. I told her, no that is incorrect that there were other fares that could be used, she insisted that I could not have used the SWU on LH unless I had booked B or Y. I was getting frustrated at her, I said that she was incorrect and said thank you and hung up. Called back a few minutes later and got the answer I was looking for, in fact had I check MP website I would have found it myself. This is the first argument I have gotten into with an agent, was not pleased that she did not have the answer, or at least try and find it for me, but then maybe she was a CO agent in "learning", I guess everyone is right, if you don't get the correct answer, hang up and try again.