Social Security Overpayment?

I receive survivor benefits for both my son and myself. They said that they overpaid me for 2014 in the amount of $5024.00. I received a letter and it did not say anything about paying it back. It actually said and I quote "you will receive $341 for May 2015 on June 10, 2015 and then you will receive $ 567.00 on or about the second Wednesday of each month. It does "not" say anything about withholding anymore money from me.

Today I was supposed to receive my son's benefits of $567.00 (we get the same amount) and instead I got a letter saying that there was an overpayment of $1134 on the record. Legally my son's benefits are not considered my money or my income. It states that on the Social Security website.

I obviously was confused about where this "overpayment" came from being as we didn't receive any extra money for my son's benefits and he had $0 income since he is 8 yrs old. I called them and they told me that the overpayment was from my benefits and they are keeping my son's benefits in the amount $1134 (2 months worth of benefits) to repay what I owe them, even though, they are already getting my full benefit of $567 a month. The woman on the phone said that they are withholding my benefits until July of 2016. They started withholding my money as of May of this year.

Now let's do the math. May 2015 to July 2016 of my full benefits of $567/mo= 15 months and a total of $8164 (they paid me $341 for May) and then now include the $1134 that they took from my son's benefit amount $8164 (me)+$1134 (son)=$9298.
I owe $5024 and they're keeping a total of $9298? Correct me if I am wrong, but that is $4,274.00 more than I owe!

First of all they are taking too much money from me alone and now they are taking $1134 from my son? There seems to be 2 problems here: #1 Someone can't count and send proper paperwork and #2 they are withholding my son's money to pay my debt, when his benefit amount is not legally my money. So they are allowed to steal from another person to payback someone else's debt that is already being paid back? Really? Someone please explain to me if Social Security is allowed to do this? I'm sure they are not and that they have royally messed up, but, humor me, please.