In order to keep call costs for cell phone calls as low as possible, there are various techniques used by call-by-call( CbC) providers. Call-through is a technique in which direct dialing via the mobile network is bypassed and the call-by-call provider switches the call via fixed-network connections.
In a call-through connection, the mobile customer first dials the fixed-network number of a low-cost CbC dial-up node. He can determine this using cell phone software. The application is used to inform the switching node of the desired subscriber number. This can be done by incorporating the desired subscriber number into the number used to ring the CbC exchange. The CbC provider forwards the call via the fixed network and collects the charges for this.