SMS is phone. I assume that CrunchSMS also uses the phone side and not data, but I do not know. You need to ask them.
Email is data. Web is data. BBM is data as are most of the IM apps. A lot of apps use data and if you don't close them out when you are finished, they keep using data until you hit the "close" button (not exit out).
Probably cheaper to get a data plan.
What cell carrier do you use? Please update your profile to add that information. It helps when you have questions like this.