Change my user name

Hi,

For some reason form settings don't allow me to change my user name. I have changed it ones right after I started using forms but it does not allow me to do it again. 

So here is the thing, I am managing this account on behalf of the school I'm working in. I was sure that the user name only identifies the name of the admin. But now I see that it also is added to my personalized links to the forms and that's not right. Can you please change it for me? I need it to be ExamMadridAcademy instead of MariyaKh. 

Thanks in advance!

Or exam-madrid-academy would be actually better

Both usernames below are available. Please confirm which of the usernames you prefer?

ExamMadridAcademy

exam_madrid_academy

Looking forward for your response.