Can I Make My 2 Yr. Contract Phone Prepaid?

I Have A Blackberry Torch From At&t And I Only Had The Phone For 1 Month And My Bill Is $697 Which Is Waaaay Too Much And I Keep Calling And Telling Them That They Overcharged Me But They Wont Listen Sooo Is There Anyway That I Can Change My Phone To A Prepaid Phone Without Paying An Early Termination Fee ?