Did you pay the child's mother informally? If so, then you can ask her to sign an affidavit of payment and submit to the AG's office. Otherwise, you will have to prove to them that you paid support.
If you have proof of payment for the child support, then you need to supply that proof to the agency if you have not already done so. If this does not alleviate the problem, then you should consult with an attorney.
Nothing in this answer constitutes an agreement to represent you in any criminal case. Additionally, the information provided above does not constitute legal advice.
You need a lawyer in MIssissippi to address this issue. I agree with the other lawyers about affidavits of direct payments but you need to make sure the administrative process is not binding on you at this point. It's very different from state to state so you need to find someone in Mississippi to help you. Good luck.
Please be advised the posting of this answer does not create an attorney-client relationship. Karen L. Marvel and the Law Office of Arthur G. Augustine, as a condition of their employment, require a signed written employment agreement prior to formally establishing an attorney-client relationship with any person.