Mac App Store Update Problem

I can not update already pre-installed mac apps in the mac app store. The apple ID is an incorrect one and it shows up as grey and doesn't let me click it and change it. I have tried restarting my laptop and signing in and signing out of the app store. I have also tried recreating a blank receipt in the contents folder for the given application and nothing seems to work. What do I do?

Go to My Apple ID -Apple Support and see if you can still log onto "Manage your Apple ID". If you can not log onto your traditional logon then your account has been hacked! Then Call Apple Suppport ASAP!