apple id and app download problem

I'm trying to download purchases and app updates on my iphone 4s and when it asks for my password and hit ok another id/password box pops up and someone else's apple id is listed and it's asking for the password. I cannot get any further and apple support has been no help. I tried resetting my password, logging out of the store and back in and still no luck. Help! The apple id that pops up is my dad's id but I have never logged into anything using his id so I don't understand why this is happening.