Can a person on ssd be sued for non payment to a person that help them to receive ssd. Also they sign a contract and gave me poa.

You can sue whomever you'd like. Winning is an entirely different matter, and collecting from someone on Social Security Disability is another hurdle. Small Claims court is designed to be user friendly, and you can file the paperwork yourself. Please note that as a Social Security Disability Advocate, you are required by law to work on contingency, and can only charge 25% of the back pay award your client receives, up to a maximum of six thousand dollars with some additional out of pocket fees.