I bought a used iphone 5S at a second hand store to use as a spare to my 7+. It's locked, so I'd like to do a hard reset. I've been reading online about how to do it, but it seems every webpage says it either has to be connected to itunes through a computer or it has to be done with some third party software. What am I missing here? Isn't there some way to hard reset without itunes or a third party app?