In the state of Florida, payments for child support were willingly paid until 21st birthday. Child is now seven months past that. I asked the state to stop payments, but it's taken them seven months and no confirmation it will stop yet. I asked ex-wife for some money back which she gave one time and very little; acted like I didn't deserve it. QUESTION IS... do I have a legal right to the overpayment (JAN until they finally stop)?

Who is taking the child support from you? Is the money being garnished from your wages by the Child Support Enforcement people? If I were you I would definitely go sit in whoever's office that is garnishing your wages and talk to them about it. Do you have a copy of your Divorce Settlement paperwork which shows how long you were/are supposed to pay child support? Take that paperwork with you.

In some states (like Ohio) the father must obtain a signed Order by the Judge terminating any child support payments after the child reaches a certain age whether it be 18 or 21.

Don't expect "them" to do anything with a phone call from you. Go there in person and demand what they need (paperwork wise that is) to STOP the garnishment of your check.