Iphone 4 activation problem ( I have the original id and pass)

Question

     Hello,
     After the update to 7.1.1, my iPhone asked me to activate it. I encountered this a few times in the past but it didn't matter because I do regular back-ups so after activation I would restore it.
     I have the phone from my aunt ( first owner by a contract with Vodafone that was terminated almost a year ago, iPhone still factory locked ), and the problem is this : the phone asks for an email address that doesn't exist. What I am trying to say is that for an example it asks for an id that looks like this with a " b*****@yahoo.com ", and the actual id that was firstly used on this iPhone looks like this " i******@yahoo.com " and was latter changed to " b************@yahoo.com " and later changed to " t**************@yahoo.ro ". The iPhone never had any other email in it ( nor iCloud, nor the store, not even in the mail ).
     Does anybody have any suggestions please ?
( I will probably have to settle this with Vodafone in the end but my aunt is currently out of the country, and I really need my iPhone to work )
Btw, if it helps, the phone was never jailbroken, and no other programs where used to interfere with it in any kind.

Answer 1

     First of all thank you for your help.
     Secondly I activated this iPhone before ( about 2 or 3 times, because it sometimes asked me after an update and I used the id I know ).
     Anyway I guess I'll have to wait until my aunt gets back in the country so she can call apple and sort it out, but I was hoping it could be a common error.
Want to know the most frustrating part ? Every where I asked they all believed the iPhone is stolen and nobody believes it's just an error. I'm really considering and android right now ...