Hello,
We are currently using Exchange Online (Plan 1) and plan to upgrade to Office 365 Enterprise E1.
According to this article, it is possible: http://office.microsoft.com/en-us/office365-suite-help/can-i-change-my-office-365-plan-or-subscription-HA104031833.aspx#EligiblePlans
How can we do this upgrade? The article above only provides instructions for upgrading from an Office 365 account, althrough upgrading from Exchange Online seems to be supported.
Thanks