You should call 1-800-COMCAST and find out what has happened. They would not remove channels without notice going out. (They would get into trouble for doing that). Its possible it has moved to the next level or gone digital (and you dont have a box to decode it).
Oh... sure... stay on hold for 20 minutes and they won't have an answer. I came on here searching for why they took G4 off my lineup last Fall and still list it on their site as channel 073... all these months later. Why doesn't Comcast update these listings on their "What's on TV" site?
sigmund The channel lineup I'm looking at for Ann Arbor is showing G4 on channel 73 and / or 162 on digital starter. If you don't have digital starter and a digital set top box that's why your not receiving it.
And for meechigan, Style channel in Ann Arbor is showing up on channel 68 and / or 118, again on digital starter. The listing shows both channels, possibly because they are changing it's position.
If you were getting it on extended basic before, then they moved it to digital starter. Moving channels between tiers is common, and notifications are usually in your monthly statement.