I personally have never had a problem with verizon service, I love em (their prices ehh, not so much).
I've only received one spam text. When asked about it, I was told about their investigation on the matter, as many other people got it, and it has not happened again. I've had their service for a good 5 years, ever since getting a cell phone.
More than likely, if you call them about it, they will explain it to you. Either that, or take the charge off.
Like another member said, did you sign up for any form of text messaging? You said it was on a line of it's own. Did it also have a price? Is your bill 9.99 over what it SHOULD be (with everything you are getting).
I've never been nickel and dimed, or been hit with suspicious fees from verizon.
Keep us updated!
-A happy verizon customer