Modem only VMG8825-T50 & ASUS RT-AX88U Router

Hello everyone.
I've just had fibre installed with VoIP and been given a VMG8825-T50. I previously was using a very old Virgin Media router with the amazing ASUS RT-AX88U.    I've accessed the admin console and change the VMG8825 vdsl to bridge and turned off the firewall as per the online instructions. This did pass ethernet to the Asus but I could not access the Asus at all to set it up as the new wifi and ethernet router.   Wifi was still active on the VMG8825.

I only need the VMG8825 to be a bridge and keep the VoIP service active.

What do I need to do?

Thanks in advance.