SSA review: Disability benefits

I received a letter stating my disabled son was overpaid by $24000 dollars. SSA did not do his pay stubs correctly. They included monies that were not to be added to earnings which resulted in a smaller check and repayments of benefits. When establishing the saga they were only suppose to add up earnings only. On my son they added vacation,sick pay and other things that should never been added to established the sga. They refused to listen to reason or to even go back over the stubs. They were extremely rude about this issue. Thankyou Patricia Lewis