Is there anyone who has been notified that you owe and overpayment? I DESPERATELY need some advice.

Basically, what has happened is that I have been receiving SSI for my son. I always reported changes in a timely manner like I am supposed to. A month or so ago (I am on my second appeal) I got a letter that I received too much money and have to pay it back. NOW the last letter I got stated that I "did file all changes in household income in a timely manner" but that I am "expected to know that the amount was incorrect". What the heck! Basically they are saying that you were right, we screwed up but you should have known better. First of all, if these people would do their darn job then this wouldn't be a problem; I am not responsible that Jane Doe at Desk #2 got my letter and didn't enter it into the computer. Where does our obligation end? Is it not enough that we are living our lives with a disability? My most recent letter to the SSA stated that overseeing the job of the SSA is not a requirement of eligibility and that just because they screwed up doesn't mean that I have to pay it back because I didn't catch it. Am I in the wrong here because I feel I am so right?

I would love for anyone to share any information as far as references to statues, laws or anything that I can use or quote in my defense as far as right's and responsibilities. Supposed I was illiterate? Suppose I was physically unable to fully understand correspondence from SSA which many people with disabilities are? I guess I would be responsible for overpayment because I don't understand their "calculus-like" formula that they expect you to figure out on the back of your statement. Sheesh!

If anyone has any help or advice I am completely open to it. Thank you for reading this and I look forward to your reply!