How to unlock an iPhone 4s if it is locked with find my iPhone?

I currently bought an iPhone online, and it came out to be locked. I can't seem to unlock it. I've tried calling the person who sold it to me, but my calls get rejected! I tried restoring it several times and it say it can't be restored due to it being locked with "find my iPhone". Can anyone help me someway, suggest a way to unlock it?
ps. I've done the "hold the power & home button" method which i then connect to iTunes & click restore but still i can't do anything:(
anyone help? I would really appreciate it so muchhhhhhh.

There's absolutely no way to unlock it except with the original owner's Apple ID and password. It is part of iOS7's feature to stop theft.

The person who sold it to you must have stolen it or found it somewhere. I am sorry to hear about your plight.

Try with restore
1. Connect iPhone to your computer.
2.In iTunes, select iPhone in the Devices list, then click Summary at the top of the screen.
3. Click “Check for Update.” iTunes tells you if there's a newer version of the iPhone software available.
4. Click Restore.

if that wont help you try with recovery mode
here is tutorial