Did you recently change from a phone that had mobile web, email, VCAST, or VZ Nav?
If you did, those are automated messages noticing that you no longer have those features active. It's some weird glitch from upgrading from the old plans to these current plans.
I received three the day after I activated my DINC. Turns out it came from Mobile Email, VCAST, and VZ Nav for me. I replied "stop" to each and called VZW to make sure it stopped those features completely.