If the server is a "Root Server", you can use the 30-day money back guarantee to cancel one of the servers in your customer control panel. This guarantee does not apply to the "VPS" product line.
Assuming there is a genuine mistake, contact support again. Note that it's past 17:00, so regular support isn't available until tomorrow (emergency support costs extra if the mistake is on your side). Monday is a national holiday in Germany.
This is a customer forum. There isn't much anyone here can do for you.
(Das ist keine Frage vor dem Kauf und auch keine Frage, die irgendein Kunde wirklich beantworten kann.)