To be sure that no other application is using your data/connection, follow this:
Go to Options
On every app, select Edit Permission
Then on Connection, select Deny
About the email thingy, I do have that option on my Setup Menu.
BBM requires mobile data to be turned on. You just have to make sure that other apps that use data are turned off so you will not incur additional charges.
Follow the instructions provided by @notevenfollowed