902 Mobile is a virtual number in which calls are diverted to a mobile number. In this way, you could receive, on your mobile, calls received on your 902 number with a very reduced cost per minute (from 0.078 € / minute).
If you would like, you can rout your calls to a fix (in order to save up the routing cost) when there is a fix where you are (office, home, etc).
You do not need any special equipment (switchboard, systems, etc.), only a mobile where you could receive calls.

The call cost to 902 numbers is completely carried out by the caller, you only pay the routing to your mobile.
This system operate with prepaid system (you must have a pay on your account to use this service).