If you want this permanent , just cancel your phone plan and keep the BB Data plan (call nextel support)
Or if you want to keep your #, but not receive any calls
-> Nextel should have a "do not disturb" # you can call (like *78) which automatically sends all calls to your voicemail
-> OR you can call forward your calls to another number so no calls will get to your BB
lol very interesting me and the blackberry technical support found the feature by accident. if you go into your profiles and click phone there is a do not distrub checkbox. works wonders. I wish the blackberry had this feature like other nextel phone do, That if the person isnt on your phonebook it wont allow the call