Samsung SPH-A600 User Manual page 156

When is my data connection dormant?
If no data is received for 10 seconds, the connection goes
dormant. When the connection is dormant, voice calls are
allowed. (The connection may become active again quickly.)
If no data is received for an extended period of time, the
connection will terminate.
Can I sign out of data services?
You can sign out without turning off your phone, however you
will not be able to browse the Web or use other PCS Vision
services. While signed out, you can still place or receive phone
calls, check voicemail, and use other voice services. You may
sign in again at any time. To sign out, go to Settings/Internet/
Sign Out in your phone's menu.
Section 3: Using PCS Service Features
3B: PCS Vision 148