Embodiments of the present disclosure are directed to a switching method and a switching device. When a mobile terminal needs to be switched from a first communication network to a second communication network, detecting whether the mobile terminal is in a ringing state. When the mobile terminal is in the ringing state, detecting whether the mobile terminal is switched from the ringing state into a connecting state within a predetermined time period. When the mobile terminal is switched from the ringing state into the connecting state within the predetermined time period, performing an IMS registration through the second communication network to connect the mobile terminal to the second communication network.

A system and method for integrating an existing telephony system of a business with various other existing communication equipment in a unique sequence and using call servers to facilitate voice calls to be made over data networks between businesses and customers for the purpose of low cost customer service provision. The system and method comprises a business connecting voice calls over data networks to customers registered in a dedicated directory using a digital to analog converter to convert the existing telephony system format of the business into digital format to transmit digital packets to the call server which will function as a telephone switch and connect the call to the customer and customers making voice calls over data networks to the business using the directory. Customers use a computer or mobile application which transmits digital packets to the call server which will connect the call through the converter, converting the format from digital to analog, to existing telephony system.