Contract owner change and new credential

Dear o2 team,

I have recently taken over the contract of my previous landlord for the Internet and phone.

I have accepted the offer and have received my first invoice from o2 on my email address. 

I have the following piece of information available: Auftragsnummer, my landlord´s old Kundennummer, my own Kundennummer, the Festnetz and that´s it.

I have not received any PKK since i have taken over the contract of my landlord.

However, I wish to access my o2 personal space but it seems like my email address, nor my kundennummer or Festnetz nummer are registered or valid.

How could i fix this issue as it seems that none of these info are valid or registered anymore.

Thank you

Best regards

Geo