payee help

yes I was my son's payee for the first few months of him getting ssd. All of a sudden his dad became the payee. So I went to the office, and they said that he said I was in jail for a few months. I have never been in jail.. Isn't that fraud? We have split custody, and when my son is at his home, he doesn't take care of him anyways.. His parents do. He doesn't do the parenting things a father should do.. I don't understand why I am not my son's payee, and how my x husband can say what he wants and they automatically swith it to him. Also amazing how he has a new truck all of a sudden. What are my rights? What can I do? And the social security office never even sent me a letter stating they were switching the payees. And my son's dad didn't even want me to get him ssd. Iam the one that took him to the hospital, the doctors, and his disability appoitments. I don't understand. i take care of my son. thank you