I would get with support on this, I had some trouble activating my new iPhone 5S and they were able to walk me through a series of steps that basically reset the network connection for the phone. I believe it was Settings > General > Reset > Reset network settings. This may help you, but to be sure I'd call them and ask.
Good thing this VZW sleuth is on the job and ready to crack this case. Now, there could be quite a few different reasons as to why this is happening so I've got to ask a few questions. First, did you have another iPhone before your current 5s? Are these other non-VZW users on iPhones or a variety of different devices? And just to be sure, what's your zip code?
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