Go to Settings > Wi-Fi.
Find your Wireless connection which has the tick or checked mark and click on the blue 'i' icon.
Note: On older version of iOS, the icon should be a blue arrow.
You should now be in your Wi-Fi details page. Tap on DNS and delete the existing DNS address on your device.
Now tap on the Wi-Fi button at the top left of your Wi-Fi page to save the changes and go back to the Home screen.
If you have any problems or can't get connected, please email us at firstname.lastname@example.org, and try to include any errors and a full description of the fault.
We'll get back to you as soon as possible to assist you.