It sounds as if you are the representative payee for the child. We are not experts in representative payee matters, but this sounds odd.
Social Security directs that you must first use the benefits for "food, shelter, clothes, medical care and personal comfort items".
However, the SSA also directs that you must, "Save any money left after meeting the beneficiary’s current needs in an interest bearing account or savings bonds for the beneficiary's future needs."
You may wish to seek an appeal for this.
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