As the question states, I'm trying to translate “They mistakenly charged both the school and me for the same thing.”
According to this link (https://ejje.weblio.jp/content/%E5%90%8C%E3%81%98%E4%BA%8B), “The same thing” can be translated as 「同じ事」.
Also, according to this link (https://ejje.weblio.jp/content/charge), the example “He always charges me too much for his goods,” can be translated as 「彼はいつも品物に対し高すぎる値段を請求する」. That example seems to come pretty close to my question.
However, I am stumped with “Both the school and me”. I've looked at the different translations for “Both” and “And”, but they don't seem to cover the situation I have.
Do you know a good way to translate it?