Occasionally, the issue is with the wireless network itself, which becomes corrupted and unstable. In this scenario, all you have to do is forget or erase the network and then add it again on your iPhone to solve the problem. Here's how you do it:

1. Go to the Settings menu.
2. Select Wi-Fi.
3. Select your wifi network by tapping. Make a note of the password for your Wi-Fi network.
4. Next to your Wi-Fi network, tap the blue I or information symbol.
5. Choose to Forget This Network from the drop-down menu.
6. Return to the Settings-> Wi-Fi menu after a few seconds, then scan for accessible Wi-Fi or reconnect to your existing Wi-Fi network.