I know that in a broadband network a virtual circuit is established like in an X.25, frame relay and ATM. Is there a virtual circuit established in narrow band network and if yes then how is it established and maintained?
Your question is extremely broad, possibly due to some mixup.
All forms of ISDN use circuit switching, so channel resources are allocated for the entire duration of a connection. The various ISDN flavors use different kinds of B-channel signaling protocols, like DSS1 or Q.931.
A virtual circuit is (more or less) an emulation of a circuit-switching network over a packet-switching one. For instance, TCP can provide such a virtual circuit, or X.25.