Your iPhone's Settings Menu Options
Check out your Wi-Fi options.
Wi-Fi is typically the fastest wireless network you can use to surf the web, send e-mail, and perform other Internet tricks on the iPhone. You use the Wi-Fi setting to determine which Wi-Fi networks are available to you and which one to exploit based on its signal.
Tap Wi-Fi, and you see any Wi-Fi networks in range.
A signal-strength indicator can help you choose the network to connect to if more than one is listed; tap the appropriate Wi-Fi network when you reach a decision. If a network is password-protected, you see a lock icon.
You can also turn on or off the Ask to Join Networks setting. Networks that the iPhone is already familiar with are joined automatically, regardless of which one you choose. If the Ask feature is on, you’re asked before joining a new network. If it’s off, you have to select a network manually.