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It is firstname.lastname@example.org
That device is just a router, not a combined modem/router, you need a standalone modem as well.
There are not many choices of standalone modems, your choice is a used Openreach HG612 from ebay, a Draytek Vigor130 or a Netgear DM200. Various Zyxzel devices can also be used in bridge mode.
You might want to consider a combined VDSL modem/router instead.