Save the $$$ on messaging!
Here's an option to save the text charges. I just got my Google Voice number. There is an app for BB that lets you use GV from your BB. This includes sending SMS via Google. You do not have to have SMS service on your BB in order to use the Google Voice SMS. Hence, free SMS. You can't do MMS from it but if all you require is texting and don't want to pay $20 a month, it is definitely an option.
Since Google Voice is new, they are rolling it out slowly. You can register your email with them and they will notify you with an invite to join. I only waited about a week before I got mine.