How can someone put their number under someone else's name in an iphone without touching the phone

Question

Ok, so last week on saturday my wife called and asked me why I facetimed her.  Well I never facetimed her and didn't have an accidental call to her at all.  I didn't think anything of it.  Well later that day she called me again very upset saying there someone facetiming me from your number and it was someone elses picture on the other end.  So we called sprint and they reser our  network setting and said call apple support.  Called apple support they said change all passwords and sign up for that duel security option.  Well no one asked us to have her look in her phone and see if there's another number in her phone under my contact info.  So I asked her to look and what do you know there's another number under my contact in my wife's phone.  Now theres no way she accidentally added in a number to my contact.   We know the face and name of the Asian Indian man who called us because sprint told us his name and we've seen his face because he facetimed and my wife saw his face.  We don't known him at all.  The weird part is that the number hes calling from is the same area code that we live in.  So that makes it extra creepy.  We figured he hacked in some how and was sitting somewhere in Asia....  I hope this all makes some since to someone who can tell us how my wife's iPhone 5s contact list was changed by a man who is phone stalking her???

Answer 1

It can't be tracked by serial number, if can only potentially be tracked via Find My iPad - if that has been disabled, as you say in your post, then you won't be able to try and locate it.
You've reported it to the police ? If your iTunes account info has been changed then you should contact Support in your country so that you can try and get it back : Apple ID: Contacting Apple for help with Apple ID account security
You should also change your email account passwords, and any passwords that you'd stored on websites/emails/notes etc.