Underpayed Back payment!

My mom faught long and hard for 4 years struggling to receive SSI. in feb 08, she went infront of a judge after being denied, they granted her SSI. My mom received a letter feb 28 08 stating she will receive 22,000 dollars back payment not including lawyer fees. to my knowledge the lawyer can only take 25%. Anyhow, she passed away March 6th. After a long hard fight. Now I have been turning in all sorts of forms since I am entitled to this money. They lost my form! I had to take off work many days to go up to the office, they found they screwed up because a rep even stamped and made a copy of the day I turned in my form. Anyhow..now a year later..I receive a check for 6,000? Where is my other 10,000? they didnt write any reasoning for my shortage and I am livid at this point. How can they short me 10,000? I call the lawyer that represented my mom but he does not return my calls, is he still entitled to fight this with me or is his case a done deal? If anyone has advice please email me.. sadeebrown @ yahoo.com I have many questions and do not know much about SSI at all. I just know I got screwed!