A refund of any "unearned" fee is going to be determined by the language of your attorney's fee agreement and the local rules of your state bar. In Criminal law, attorney's are allowed to have a non-refundable retainer fee, but that fee must be earned, meaning they did some form of sustainable work to justify the fee. Not certain what your attorney did or did not do to have the charges dropped, but I would contact your attorney to determine exactly what work was performed on their part to justify the fee.