My expereince is that special rate plan code rooms rarely show up on the listing online, but the agent can find and book it when I call. I rarely consider calling unless I'm already aware of the special rate code and can't find it through an on line search, as I usually shop for the best value I can find online. But got quite lucky just this past week when I wanted a particular hilton and decided to call because I wasn't thrilled with any of the online rates and ended up saving $33/nt. for a 2 night stay.