Hello I have tried already but have not been able to resolve the issue. 

Is it possible to change the username for an account ? 

Hi:
We have not supported to change the username after register yet.

But if you really want to change it ,there is a flexible approach.

1 delete your device in this account(if there is only one meter in the place ,delete the place directly)
2 delete your email (please refer to the below pic)
3 register a new account with your wanted username,SN and the email again,