How to turn off Edge Network and use "WiFi ONLY"

[Proteus]

Please help in solving a very small problem which I am facing. Recently I bought an Apple Iphone 3G. I was able to access Internet on the phone using EDGE network and Wifi but from few days I am only able to use the EDGE network for connectivity to internet. The phone does not use Wifi anymore. So I want to know How to turn off Edge Network and use "WiFi ONLY" on the phone. Any help is highly appreciated. Thanks in advance

[Pabloa]

The default priority of Wifi connection is higher than the Edge network connection. Hence whenever any Wifi network is available the phone will automatically start using the Wifi connection. You dont have to turn off the EDGE network manually. The display may be showing connected to the EDGE network but the phone will be using Wifi connectivity.

[Paisley007]

You can easily get rid of the EDGE network from the phone as it is dependent on the SIM card and the service provider. If the phone is not using Wifi connection by default then you can remove the SIM card from the phone and then access Internet on the phone using the Wifi connectivity. I know this is not the exact solution which you are looking for but it will work for sure.

[Proteus]

Removing the SIM card cannot be implemented as I want to keep receiving calls while I am using the Internet on the phone. Now I have started to think that there is some hardware problems with the phone. Still I want to know if there is any alternate way in which this problem can be solved? Will have to get the phone replaced?