Hey, thanks for reading in English.

I am trying to register for internet to our apartment. 

The first barrier I get is a notification at checkout:

SystemErrorMessage 

Registration is currently not possible. Your login or password was entered incorrectly. Please try again. If you have logged in using your mobile phone access data, please log in  again here.

I followed advice to log out then try again. This got me to the next step, but the form requires a mandatory landline number. We do have an apartment, but we do not have a landline number that I know of.

Any help much appreciated. Danke!