If you hadn't withdrawn your applications already you might have options but at this point you've painted yourself into a corner. You made a binding commitment to Columbia and told both the Booth and Kellogg admissions offices that you made that commitment and were admitted. So now you would be calling them back to say, I know I told you to withdraw my application but I'd like to be considered again even though I'm out of cycle. And regardless of the reason you give what they are going to hear is, I gave my word to CBS but my word doesn't mean that much and I want to explore other options now. MBA admissions are a small world and I would be very surprised if they didn't call somebody at CBS.
Honestly I don't know that you really have any good options. And even if you apply next year(which you say you can't do) Booth and Kellogg will have you as a re-applicant and will probably have a record that you withdrew your applications. I think you're in a tough spot unfortunately.
Thanks for the feedback. Yes, it doesn't seem like I have any good options, so I am just going to matriculate to Columbia and will try to get a summer internship in Chicago.
Like mentioned before, CBS was my first choice for the get go and I am really excited to start the program next Fall.