Trial Account Lockout

I just set myself up with a trial account for MS365 Business Basics. Of course it demanded that I set up a .onmicrosoft.com account name/email address. Then it asked me to sign out (which I did). But after that point it refuses to acknowledge the email address in question, "This user name may be incorrect....". So now I have signed p for a trial account but cannot log in and at the end of a month I will probably be charged for it. I am not at all happy but have tried everything I can think of and have now even joined this forum!