It appears to be a Vodafone secret. I can't even find a proper manual for the router which explains all the options.
If you have a dongle you could try just plugging it into the USB port and then disconnecting the phone line from the router. If you then try to access an internet web page from a connected device you might get a web page where you have to select 'Connect'.
I have a Zyxel VMG8924-B10A and that was all I did. Like the Vodafone router, the Zyxel router did have fields for parameters shuch as userid, password, APN etc to be entered but I did not need to use them.
If your broadband connection fails you might find it easier just to use a mobile phone wifi hotspot,
