Devices are essential for cloud phone. There are two ways to use the devices. You can subscribe to devices and get the devices all to your self or you can rent a device as needed with the pay-as-you-go option (The rental device will be billed when it is connected to an environment).
Navigate to Subscription - Cloud phone devices tab. Click the Purchase devices and you will be directed to a secondary page.
Here you can select your device, choose how many devices you'll need, and choose different subscription periods to enjoy different discounts.
There are various payment methods available as well.
(The price may subject to change.)
After subscribing to devices, you can view their status (idle, or being in use).