Apologies for the rather naive question. I'm not a frequent UA flyer, but have a work-related trip booked for me by a US gov TA. The itin is UA out and AS back. Since I don't have status on UA, I wanted to use the paltry $25 I have in my UA travelbank from an IHG card to select a better seat, but the option doesn't appear for me (on app, or website): only allows for use of CC/paypal or travel certificate.

Is this because it's a TA-booked itin, a mixed airline itin, or both? Will calling United help?

It's a fairly short hop, but I am in literally the back row, and wouldn't mind a sl. better seat for essentially 'free money" that would otherwise go to waste...

Help/advice appreciated.

tb