Auto-disconnect connection

[Daved]

How do I get the apache to disconnect from the Internet after a period of time?

It stays connected for hours and drains the battery and I don't get calls.

This is because I'm on an 1xRTT area with simple ip only and while I'm connected I cannot get calls so I need my apache to work like every other CDMA phone, after an specific period of time it should disconnect automatically and reconnect when it's needed.

How do I do it?

Thanks in advance