Instant upgrade Dual inventory fares are available in all business/first class booking classes (except maybe J). It's pretty common to see them in P, Z, D, and C.
Having said that, you're entitled to be rebooked in the premium cabin. Some agents erroneously believe otherwise, and trying to convince them that they're wrong is usually an exercise in futility. Your best bet is to hang up and call back.
Last edited by Sykes; Jun 18, 2019 at 3:37 pm
Reason: They're not instant upgrade anymore, they're dual inventory.