Is this for today? I'm assuming you're on UA37 LAX-SIN, since that's the only 17 hour flight UA has from LAX. If so, it looks like every seat is full, which really doesn't look good for getting the GA to swap anyone in advance. You may have better luck on board asking someone to swap like-for-like.
Were both of you moved? if just one of you got re-seated I'm assuming a FAM, and there's not much you can do about that...