dont allow to create contato@ user

dont allow to create contato@ user

I create a free account at zoho to the domain cppsaude.com . , with the superadministrator the mail administrador@cppsaude.com

Now i what to create another user called contato @cppsaude.com, but the tool sad that is not possible because this account is already exist. but it not appear the de mails accounts. If a try to create another emai like ""atendimento@cppsaude.com" it's allow, but contato @cppsaude.com inst's 
Could help me?