Anyone know the magic word(s) for this? I find it's really useful to use their terminology.

I'm on 612 LAS-DFW-BOS in a few weeks. I've called several times to ask if they can "break" 612 into two distinct segments. Every agent has said no. Looking at the PNR online at aa.com both "segments" of 612 show at the top with the arrival/departure info. But under the Upgrades section it has only a single entry LAS-BOS; same thing for the seat map - LAS-BOS.

I really want it to post as two segments not 1, and there are far better seats available DFW-BOS than LAS-BOS; I'd like a better seat for the longer segment.