iOS7 has a security feature that, if someone steals your phone and tries to restore it to a new ID, you'll need the old ID/Password. This esentially bricks the phone.
You will need to enter your old ID and password. If you cannot remember your old ID and password, you will need to contact Support and have it reset. They will need to verify your identity with your security questions, DOB, credit card, or a Temporary Support Pin.
Here is more info on the iOS7 Apple ID activation lock
If the request Apple ID is one you had previously go ahead and enter the Apple ID and it's password. Once you get the phone's activation lock cleared you can set it up as new with your current Apple ID and password. If you forgot your password for the old ID visit this Apple support page: