How to delete an account


I have made an acccount by accident while trying to get a new account from my school, they want specificly the name that I was told to use and now when I am trying to get into my school account, Hooktheory wont let me becaus I am trying to choose a name that I accidently already had choosen for the other account that I made by mistake.
How kan I delete my account or just change my name so that I can put it on my school account.
//Best regards.