Travis did eventually hear it when Charlie screamed for help. So did Mr. Maloney. Of course, I didn't bother including these in the epilogue as you'll see soon enough.
As for Jared? Well, some people are just plain crazy I think.
I actually did include my name in the plug in the first draft. However, I decided to tone it down after a discussion with one of the beta readers.
And no, Charlie does not have a cellphone. If you can recall, it was broken when Luke attacked him in the junkyard. Similarly, Derek does not have a phone. It was also broken when he slammed his fist on the kitchen table.