You can turn off and on your data plan by going to Verizions web site. It's under:
My Phone > Add/Remove Features > Multimedia
Or the direct link is:
https://ebillpay.verizonwireless.com/vzw/accountholder/account/maint-features.do
You can disable/enable V CAST Music, Mobile Web, Application Downloads, and V CAST Video Clips without having to contact customer support.
Also this does not disable MMS/texting. I haven't tested wifi yet as my card just came in today but I'll update later tonight.