BlackBerry Bold 9000 text function not wor...

Hi from Australia...My BlackBerry Bold 9000 will not send text messages....all other functions ok...including incoming text.
Other folks have same problem as listed in BlackBerry Support Community Forum.....you can re-boot..battery out ...sim card out....
and spend hours talking to tek people who guide you through a million configurations and problem allways comes back.(it will work after battery out re-booted etc but problem allways returns
It was good to see the posts in blackberry.com.....and know i am not alone.
However ...i would really like to know how to fix this
Cheers Chris