How is it possible to downgrade the contract plan/tariff?

Hello!

I have 24 month contract plan “O2 Mobile XL (2024)” started in 14.11.2024 with a notice period of 1 month(s) before the end of the minimum contract term.

What are the downgrade options in my case?

On the website, under the “Zur Vertragsverlängerung” sometimes it shows several options to upgrade/downgrade, sometimes options are not loaded at all. It is difficult for me to find time when it properly works, in order to choose right tariff.

How is it possible to downgrade the tariff earlier then after 12 months only, and what will the options in my case?

Thank you!