Social Security overpayment penalty?

Unfortunately, your situation is apparently fairly common, both with SSI and SSDI benefits.  In some cases, the SSA has made an error regarding the existence of an overpayment, and the recipient should file an appeal or a "Request for Reconsideration." You must file the Request for Reconsideration at your local Social Security office within 60 days of receiving the "Notice of Overpayment."  For purposes of calculating the 60 days, the SSA will assume that you got the Notice of Overpayment within 5 days of the date printed on the notice unless you can demonstrate that it came later. 

In other cases, such as yours, there was an overpayment, but the recipient may feel, justifiably, that he should not be held responsible for the debts.  In that case, it may be appropriate to ask for a waiver.  It sounds like you did everything you could, including keeping a record of the name of the person you talked to.  Ideally, you will also have a record of what was said during the conversation.  Because the stakes are high, you may want to contact an SSDI attorney to help you with the waiver request.  You have the burden of showing that you were not in any way at fault.  You must show that you did not provide false information, did not withhold relevant information, and that you should be allowed to keep the overpayment because you are unable to pay it back and/or you acted in good faith when spending the money on normally occurring family/living expenses.  In other words, you did nothing wrong, fulfilled your obligations, and relied on the SSA to notify you of any changes in your eligibility.  Hope that helps.