Communication system and method thereof

A communication system used for enabling a caller side communication device and a called-party side communication device to communicate with each other, wherein the called-party side communication device comprises a first communication module and a second communication module, the first communication module and the second communication module respectively support a wireless local network communication and a mobile network communication, the communication system comprises:

• a virtual secretary system for judging whether the called-party side communication device is inside an area of a wireless local network and determining whether to establish a first communication link on the wireless local network for enabling the virtual secretary system and the first communication module to communicate with each other or to establish a second communication link on a mobile network for enabling the virtual secretary system and the second communication module to communicate with each other;
• and
• a business telephone system for enabling the caller side communication device and the virtual secretary system to communicate with each other in response to a ringing event;
• wherein, when the caller side communication device and the virtual secretary system communicate with each other, the virtual secretary system further establishes one of the first communication link and the second communication link for enabling the caller side communication device and the called-party side communication device to communicate with each other;
• wherein, when the caller side communication device and the virtual secretary system communicate with each other and the location of the called-party side communication device is switched between being inside and being outside the area, the virtual secretary system, by way of multi-party call operation, switches the first communication link to the second communication link or switches the second communication link to the first communication link, such that the caller side communication device and the called-party side communication device keep communicating with each other.