I booked a one-way ticket last week in W, and since then UA changed the fares in that particular market so the lowest round-trip is S but the lowest one-way is H. I called and the agent offered to add the return fare in S to my original ticket to create a round-trip ticket with no change fee. Is this standard practice or did I get lucky?

Edit: actually it's even better -- the outbound also got refared into S! Must have gotten lucky.