Iphone 5 in demo mode

Some one recently sold me a Iphone 5 Working display model phone, at
the time I did not know nor did he comment it being so. These are the
same phones that are on display at a carriers store, they fully work and
can make calls and all that...

I stuck my sim inside and it fully woks from what I seen so far But its
In some demo mode, I want to restore it so I can get it off it's demo
mode or what ever it is.


Here is my problem I want to get this phone out of this demo mode so I
can fully use the iPhone like its a normal iPhone.. I'm scared to
restore the iphone from recovery mode or dfu mode cause it might lock up or
something. has any one did a restore and was successful