Yes, vision is the data service, but its not free for everybody... Did you sign up for a SERO account? Those have it included. Maybe they had another package you signed up for. Hopefully, they don't catch on and then slam you for a charge. Non vision package phones CAN use the internet, its not blocked. They just pay something like $0.03 per kb. Which can really add up. Anyhow, if you are out of contract and aren't looking for a family plan, you should look at the SERO offers:
www.sprint.com/sero
You can use the email address
savings@sprintemi.com