A certain degree of persistence, insistence and patience worked for me to get a partner F redemption booked that couldn’t be done online (an originating city for a J connector flight couldn’t be done online even by itself).
I was booking this less than 48 hours out and was told on the phone that they didn’t have any redemption agents available, but someone could call me in 48-72 hours. Of course I said that wouldn’t work. I needed to know ASAP as a bunch of other travel depended on this getting sorted.
Next they said they’d try to see if someone would be available within the next 3-4 hours, and took all the flight details I already had ready from trying to book online. I said that would be better than nothing, and waited on the phone.
After a long time more, they told me someone would be finishing a call in the next 30 minutes and could handle me after. I said “that’s great!”
I waited a bit more than that, and finally someone came on and efficiently handled my request.
I’m not sure if it made a difference that I’m KrisFlyer Gold (thanks to some bank card transfers that gave me that status). But I was thankful that somehow a three day wait got shortened to about an hour and a half in total.

Additionally adding that I was outside the US, couldn’t get the US number to work using my VoIP app, but called the Singapore number for KrisFlyer (which, it seems, redirected to commercial sales, not redemptions).