Hi Wyslowiony, calling is currently an Amazon Echo only feature. It's not going to be available on the Sonos One for now.
You'll be able to use Alexa skills with Sonos One, and a lot of the other Echo features too, like alarms, lists, and timers. However, some specific Alexa features only work on Amazon Echo devices. The drop in and Alexa calling and messaging are such features.
The Sonos One will get news and answers, manage your smart devices and enjoy the wide selection of Alexa skills. While it's not an Amazon Echo device, you can definitely enjoy the vast majority of Alexa convenience on the Sonos One.
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