How to delete unwanted Norton Account

When I tried to open my Norton vault this morning, it came up with a window asking me to create a new account (I don't know why - my original account is still there). Anyway, I created a new account, but then found a way to get NIS Identity Safe to recognise my old account which enabled me to use my original vault information.

So, now I have two Norton accounts, one of which I don't need.  However, I can't find a way of deleting this unwanted second account. Does anyone know how I can delete it please?