Yet to fly a leg of this trip, ticketed on DL. I called in once, had a nice rep who forwarded it to the rate desk, after 20 minutes of holding, I was told that I had already done my one-time change and any other change would make me pay the change in fare. I said I would think about it and call back. Called back a few days later and got a even nicer rep who processed the change herself and said that she would waive the small difference in fare because I'd been on hold for more than an hour. As always, HUCB.