It's actually called a "waiver" and from time to time it doesn't come up in the UI for me and I have to call in. I started to wonder if either "it was me" (namely they saw I used it and didn't want to offer it to me!) or it was the city pairs. But I called in and they have always been able to add it on and book the flights I found online. There are rarely, and I mean rarely, flights at this price with anything less than a $500 cancellation/refund fee, and most have only the opportunity to rebook after a $300+ change fee. The $129 is well spent.