Why not consider unlocking that account instead of requesting its deletion? Given the account's age, there might be some value in doing so.
I'm not sure about the exact requirements and what needs to be done, but have you tried sending an email to the provided address?
Given there is a dedicated team handling recovery of accounts, I think it's very easy to unlock it, but the current account they are using is equally old and has even more activity than the other.
I am suggesting they try contacting admin to change the username of the current account to eXch.cx. I think their reason is valid enough for the admin to act promptly. Meanwhile, they can also recover the other account as back up