How to reset the network settings on my Apple iPhone 5S
If you encounter problems with your data connection, or other wireless connections, you can reset the network settings back to default. All of the network settings on your Apple iPhone 5S will be reset, including those for Wi-Fi, mobile data and VPN.
1. Touch Settings.
2. Scroll to and touch General.
3. Scroll to and touch Reset.
4. Touch Reset Network Settings.
5. Touch Reset Network Settings.
6. The iPhone will reboot. Once it turns on, the default network settings will be restored.