My iPhone 4s was recently stolen and I immediately changed my Apple ID password. Now I have an iPhone 5 and even though at first they asked for my regular Apple ID to restore backup, after then another Apple Id appear and I don't recognized it at all. When I want to download an app, the Apps store asks me for both Apple ID accounts.
The question is little unclear.
However, if you want to get rid of Unknown Apple ID, sign out of iTunes & App Stores and iCloud from your phone:
Settings > iTunes & App Stores
Tap the very first
Apple ID: firstname.lastname@example.org
Similarly, in order to sign Out from iCloud.
Settings > iCloud
Sign Out which is at very last.
And now try logging back in using your APPLE ID.