Why doesn’t E.ON pay back the money I paid too much?

I paid 47 euros too much on January 21, 2022. I immediately wrote in the chat and the employee said he would transfer it back immediately. To date I have received nothing. When we asked several times, the system always said it was there and then or it was already transferred or we had problems. I’m really getting angry. It’s not that difficult to pay back the money. How long should I wait, I would like to clarify it in good terms.