It almost appears (from what he's told me over the phone) that when he tries to swap to another username+password (for another ISP), it reverts back to <username>@xtra.co.nz - ie it appears the modem is hard-wired to only connect to xtra.
Is this correct? If so, are there any work arounds?
If I was physically in front of the modem I'd experiment with it myself, but I was hoping somebody here might be able to point me in the right direction. I tried getting him to go into the advanced settings section of the modem, but there didn't appear to be anywhere in there to change the username and password.
Thanks for your help.