They reached out to me and said it was a computer error and adjusted my overall charge. So I have changed my score. You can read my issue below:
I normally rent with National/Enterprise but because a friend recommended I went with Sixt. I was convinced that my total 770+ euros covers everything including full insurance and all the miles I need. Then after few days after the rental was over I was charged another 150 euros for miles. Be careful when you rent with them.