You can turn off BlueTooth by either going to Settings-->Bluetooth, or touching the BlueTooth icon in the Control Center (swipe bottom to center to bring up the Control Center).
Test your WiFi. If it doesn't work, double-click the Home button, locate the program BlueTooth is running, and swipe it to the top of the screen.
Test WiFi again. If it doesn't work, power down; wait 5 minutes; and power up your phone (if you don't see the white Apple icon when powering up, you did not power down properly).
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