Can another Wi-Fi connection affect my iphone5's Wi-Fi?

A friend connected his home Wi-Fi to my iphone5 and now my iphone 5's Wi-Fi won't connect to my phone. My Wi-Fi is on, but won't connect to my whatsapp or anything else. What can I do? I have reset all the settings but nothing.

Added (1). I need of help with my new iphone5. My Wi-Fi on my iphone isn't connecting to anything on my iphone and I would like to know how I can have it back as before.

Iphones are dumb. USE ANDROID.