How to get Wi-Fi on my iPhone 4s?

I recently purchased an iPhone 4s from an Amazon seller. The phone got to me in fairly good condition. The only thing is that it would not find any Wi-Fi at all. I activated it to my number and so I can use my data. BUT. I can't find any Wi-Fi networks that I KNOW are there. I have a MacBook Air, and iPod Touch (4th gen.) and an iPad in my household that connect to our Wi-Fi with no problem so it can't be Apple products. I have tried resetting everything (network settings, Wi-Fi, bluetooth, the entire phone). I even went to school and it wouldn't find the Wi-Fi there either. I'm not sure what to do at this point because I'm wasting data when I have fast Wi-Fi available to me.

Seems like your wireless card Inside the phone is just out. Try to return it