Sanyo Sprint KATANA User Manual page 171

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 Sprint Power 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 > More... Data >
in your phone's menu.
Disable Data
Section 3B: Sprint PowerVision 157