I am *G on AP, trying to migrate to A3 (and maybe subsequently to MP). I am currently on the second leg of an itinerary with US. I am connecting through PHX. I have tried to get my FFP changed at each of: customer service desk, gate, lounge, and exited to check-in counter and ALL CSRs refused to change the FFP for second leg (at gate, both CSRs emphatically agreed that what I was requesting was 'impossible'). Interestingly, each had slightly different reasons why not, but I was unable to find anyone who was willing to even attempt to implement the change.

Is there anything I could do differently to get the miles credited to another FFP?

There are some other threads where I may cross-post this for input.