but the child support agency in San Antonio Texas refuses to work with be.
I find this statement hard to understand. If you are in fact ready to pay your arrerages and current dues then this "child support agency", whatever agency in Texas oversees child support collections and disbursements, makes the arrangements with you, in conjunction with the local family court, regarding amounts and methods of payment. Ordinarily they would schedule a hearing where you would present your case and then, in conjunction with the hearing officer, formulate a payment plan.