A programmable call processing system (70) provides a standard call processing process (82) performing call processing according to industry standard call models, at least one database (84, 86) storing call processing data accessible by a set of call processing state machine process (80), and at least one customized call logic program (92) for implementing extended subscriber features on a telecommunications switching system. Further, an application program interface (94) provides access by the at least one customized call logic program (92) to the at least one call processing database (84, 86) and further interrupting the standard call processing process (82) to execute the customized call logic program (92).