VnV2178B,
If your description is correct and accurate, then Virgin have been serving you (sorry, your friend
) the finest bull's excrement you can get.
Simple fact of the matter is that your iPhone needs to authenticate against their servers in order to retrieve emails (cf. config settings on the iPhone). No funky technical concepts to wrap your mind around here.
Therefore all they need to do is reset the password for that username and hey presto (if need be you can see the username being used in the iPhone settings, but not the password, for obvious security reasons !).
I would suggest continue pushing Virgin, escalate the call beyond the script reading monkeys.