Ann: SAS Completes World First Phone Calls, Instant Messaging, page-67

SAS only needs one ground station as the satellites work in a mesh network. For redundancy they will have two ground stations, I think one is in the USA (Alaska), can't remember where the other one is.
The satellite phones to talk to the nano's isn't so expensive due to the low orbit. Powering a 5V mobile phone isn't too difficult