I cant see my free previews from dish network?

in channel 102 it say free hbo preview for the weekend. channels 300-309. my guide doesn't have those channels. i can't see. im supposed to have in my guide but it's not and if i put all channels they appear but when i push on it. it says that i must subscribe to it. with doesn't make sense since its supposed to be a preview. could someone help me please. i really want to watch a movie that is going to come out in the weekend.