How do I only use Wi-fi networkd without using 3G???

Switch on Airplane Mode, that will guarantee you only use WiFi.

It's just a guess but maybe for internet it uses whichever network it thinks has better connectivity. You might want to verify that your WiFi connection is good by putting the phone in Airplane Mode and surfing a few pages in Safari.

If the WiFi connection is good try turning off 3G (Settings > General > Network). That should put you on the slower phone network. Maybe it will use WiFi in that case.

If you switch to Airplane Mode you cannot use the phone and/or text messaging.

It sounds like you're connecting to your WiFi router but the router isn't connected to the internet. I'm not a network guy but I'd recommend verifying the router internet connection from another device connected to it. If that other device is able to connect to the internet via WiFi then it's something in the iPhone connection. If the other device can't see the internet either then your router isn't properly configured to connect to the internet.

By the way - I saw your other question about EDGE. EDGE is AT&T's slower data network. If you turn off 3G it will use the slower EDGE network.

This is not normal. If you have a WiFi connection the phone should use it. If it is not then there is a problem with the WiFi setup. This is what you should be fixing, not trying to turn off 3G (which won't solve the problem anyway if there is something wrong with WiFi).

Start here: http://support.apple.com/kb/TS1559?viewlocale=en_US

and here: http://support.apple.com/kb/TS1398?viewlocale=en_US

Let us know what you find out. There are additional steps if these don't fix it.

iPhonetechsupport wrote:
I also have another question, so if the 3G/E icon shows on top of my screen, does it mean I am using my data usage even though I am not using any applications or any web brows or Emails?? Am I gonna get charged for that?

3G or E will show any time there is a network connection available. If it is actually using the internet you will see a revolving wheel next to it. Data usage is being charged against your data allowance when the wheel is turning.

If the IP address that you see begins 169.254... it means that your router is not assigning an IP address. The 169 address is created by the phone itself and is not routable. The most common cause of this is out-of-date firmware in the router. Check for the latest version of firmware for the router and if yours is not up to date download and install the latest.

Settings > Fetch New Data
Make sure "Push" is on and it's set to something other than "Manually"

It depends on what mail server you are using and how it is configured. If you are using MobileMe or MS Exchange and you set mail retrieval to "Push" it will alert you automatically when mail arrives. For any other mail server you can either set it to "manual", which will only check for mail when you open the mail app, or to a time schedule to check for mail (15 minutes, 30 minutes, 1 hour).