Q: can not turn wi-fi on the iPhone 4 ISO 7

Hello gnisten47,

It sounds like you are unable to turn on your wifi setting. If it is grayed out, I suggest these steps from the article named:

iOS: Wi-Fi settings grayed out or dim

http://support.apple.com/kb/ts1559

If you can turn on the wifi I would instead try these steps from the article named:

iOS: Troubleshooting Wi-Fi networks and connections

http://support.apple.com/kb/ts1398

1. Be sure you're in range of your Wi-Fi router (access point).
2. Tap Settings > Wi-Fi and turn Wi-Fi off and on. If your Wi-Fi setting is dimmed, follow these steps.
3. Confirm that your Wi-Fi router and cable or DSL modem are connected to power, turned on, and connected to the Internet. If not, refer to your network administrator or Internet service provider (ISP) for assistance.
4. Restart your iOS device.
5. Tap Settings > Wi-Fi and locate the Wi-Fi network to which you're connected.
6. Tap and Forget this Network.
7. Try to connect to your desired Wi-Fi network.
   Note: You may need to enter your Wi-Fi password again if your network requires one.
8. Turn your Wi-Fi router off and on2. If your ISP also provides cable or phone service, check with them before attempting this step to avoid interruption of service.
9. Update your device to the latest version of software.
10. Update your Wi-Fi router to the latest firmware2. For AirPort Base Stations, install updates using the AirPort Utility.

There is additional troubleshooting toward the bottom of the article if you need it.

Thank you for using Apple Support Communities.

All the very best,

Sterling