Trying to eliminate a user in a trial account before upgrading to professional

Trying to eliminate a user in a trial account before upgrading to professional

Good Morning,
We have a trial version and wish to upgrade to professional.  However, the first email that was entered is not associated with a user, it is just a company account.  I have tried to delete it, leaving my own account, without success.  What am I doing wrong?

Thank you,

Molly