iPhone won't connect to unsecured wifi

This article may help: Use captive Wi-Fi networks on your iPhone, iPad, or iPod touch

Join a captive Wi-Fi network

To join a captive Wi-Fi network:

1. Tap Settings > Wi-Fi.
2. Tap the name of the network, then wait for a login screen to appear. Or tap next to the network's name, then tap Join Network.
3. If prompted, enter a user name and password, enter an email address, or acknowledge terms and conditions.

After you log in, you should be able to access the Internet. Fees and other charges might apply when you use captive Wi-Fi networks. Contact the network provider for more information.

If that doesn't work, make sure you follow these steps: If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network

• If someone else set up your network, ask them for help. If you’re using a network at a company, school, hotel, store, or other free Wi-Fi location, find an employee for assistance.
• If you're connected to a Wi-Fi network but you can’t get online, try to use your Wi-Fi network on other devices. If you can’t get online using your other devices, there might be a service outage. Call your cable company or internet provider for help.
• Try connecting to a Wi-Fi network in a different location. If your device can connect, you need to get help with your Wi-Fi network. If your device can’t connect to any Wi-Fi networks, contact Apple.
• Update your Wi-Fi router with the latest firmware and make sure that the router supports your Apple product. For more information, contact the router's manufacturer.