Try the easy fix first. Pull the battery and allow for the device to reboot. See if then it works. If it does not, then you need to re-register your device with the network. See MikeS's advice in the thread at http://community.vzw.com/t5/Blackberry-Bold/Blackberry-registration/td-p/521626 Hope this helps,
I too recommend a battery pull first. If that doesn't work then we can easily fix that for you remotely. What I will do is send you a private message so I can get some info from you & resolve this once and for all. As far as other community members, the steps on resolving this issue can be found using blackberry article number KB03868. As always, you can search blackberry issues at www.blackberry.com/btsc.
Hope this helps...