Unwanted subscription charges for "O2 Unlimited Games Flatrate"

Hello, 
I am an O2 contract customer (Kundennummer: 6106197530). On my latest bill from 02.09.2026 for the phone number 017624434514, I was charged 12.99 € for "O2 Unlimited Games Flatrate". 

I never subscribed to this service, never used it, and never authorized this charge. I have already activated the Drittanbietersperre (third-party provider bar) in my account settings to prevent this from happening again. 

Could a moderator please look into this, cancel this unwanted service, and issue a refund/credit of 12.99 € to my customer account?

Thank you in advance for your help.