Your device can be activated/inactivated whenever you want.
It will increase/decrease your monthly usage.
Inactive device will keep device registration to your account but cloud connection and functions will be stopped. And also is not counted as usage.
But monthly usage will be calculated from maximum usages in your month. So inactive may no affect for current fee.
See more on Pricing.
In Devices You can find it on "Setting" to enter device setting. In tab "Setting", Active status can be changed.
Switch will affect immidiately. "Inactive" will cut cloud connection for a device. "Active" will provide cloud connection for a device.
And it will also affect for cost in a month.