Mobile number porta

Hi! I have an o2 prepaid SIM, and now I want to take my phone number to another provider. They ask me to contact the current provider (=O2).

But I can’t find a way to request MNP in my O2 home page.

I read the following page, but I couldn’t find Vertrag verwalten or o2 Rufnummer zu einem anderen Anbieter mitnehmen tab in my O2 home page