Hello @Razeen,
welcome to our community. It's great that you've contacted us here. You can easily change the direct debit authorisation yourself via my o2. Have you ever tried this?
Kind regards, Bianca

Hello @Razeen,

If it's about prepaid, use the Chat, otherwise use the contact form.

Best regards

Hello @Razeen ,

I hope everything worked out with your direct debit and your contract. We would have hoped to hear from you again, if any of the infos you got here helped you with your issue.

Kind regards, Sven