PCT No. PCT/SE96/01275 Sec. 371 Date Sep. 3 1997 Sec. 102(e) Date Sep. 3 1997 PCT Filed Oct. 9 1996 PCT Pub. No. WO97/17794 PCT Pub. Date May 15 1997A system and method of providing CCBS services over GVNS. In a network service with routing code recalculation a supplementary subscriber service involves an interaction between two subscribers. Knowledge of a subscriber access code used in a called subscriber local remote exchange is required in a calling subscriber local exchange. A subscriber access code is generated by modification of a called subscriber routing code used by the calling subscriber local exchange. The modification occurs in a transit node of the network service. An interworking problem is then overcome by providing a relay CCBS application service element (CCBS-ASE) in a GVNS transit node and arranging for end-to-end signaling to be replaced by two TC dialogs one being the calling parties LE and the relay CCBS-ASE and the other between the called parties LE in the relay CCBS-ASE.