will my data plan be charged if the 3g is off?

iPhone 4 includes Wi-Fi connectivity as well as 3G connectivity.

Wifi is ideal if you have a wireless high-speed Internet router in your home, or if you’ll be using your iPhone near a wireless hotspot in a coffee shop or school library, for example.

3G uses cellular signals to connect to the Internet. Depending on your carrier, you have or not a certain limit of data.

To limit the use of data :

Turn Data Roaming off : In Settings, choose General > Network, then tap to turn Data Roaming off. Data Roaming is turned off by default.

Turning Data Roaming off helps to avoid data roaming charges when traveling outside your carrier’s network by disabling data transmission over the cellular network. You can still access the Internet if you have a Wi-Fi connection. If Wi-Fi network access isn’t available, however, you cannot:

- Make or receive FaceTime video calls

- Send or receive email

- Browse the Internet

- Sync your contacts, calendars, or bookmarks with MobileMe or Exchange

- Stream YouTube videos

- Get stock quotes

- Get map locations

- Get weather reports

- Purchase music or apps

Other third-party apps that use data roaming may also be disabled.

If Data Roaming is turned off, you can still make and receive phone calls, and send and receive text messages.

Turning 3G network access off alone does not prevent data or internet access via the cellular network. Turning 3G network access off alone turns 3G network access off only. When 3G network access is turned off, the iPhone will be connected to the carrier's EDGE or GPRS network (whichever is available at the time) for data or internet access and for calls. If 3G network access is turned on and you are in an area where the carrier does not have 3G access, the iPhone will be connected to the carrier's EDGE or GPRS network automatically, whichever is available at the time.

To disable data or internet access entirely via the carrier's cellular network, go to Settings > General > Network > Cellular Data > Off. Turning Cellular Data off turns cellular data or internet access off entirely with the iPhone. With this off, the only way you can have internet access via the iPhone is with an available wi-fi network.

If you turn the 3G off, you can still make phone calls, texts, and FaceTime.