If you are among those that purchased an Office 365 subscription on or around May 21, 2014, you might have noticed (if you are a careful scrutinizer) that your subscription cost twice the normal rate. If you didn't notice and just click-click-click-done like most people, you might go back and take a look at the exact amount you were charged. This wasn't on purpose, but was due to a bug in the billing system. For those worried that Microsoft is modeling Office 365 after Cable TV where your bill increases every month for no reason and without any warning, that's not the case here.
Microsoft has since admitted to the issue with Office 365 billing and is working on a permanent fix. For the majority of customers the company has worked out a fix. However, there are some lingering incidents that are still being addressed. It's like a bad formula in an Excel spreadsheet.
Customers who were double billed will be refunded.
Does this mean Microsoft's Office 365 adoption numbers for May might be akilter? Just take the number of new subscriptions reported for May and divide by 2.