1. A system for deriving information associated with an unavailable telephone number or subscriber and providing said information to a caller attempting to place a telephone call to said unavailable telephone number, the system comprising in combination: an intercept system coupled to a directory assistance service, wherein the intercept system intercepts the telephone call on a telephony network to the unavailable number before initiating any action by the telephony network back to the caller, wherein the unavailable number includes non-existent numbers or numbers not implemented on the telephony network; the directory assistance service, wherein the directory assistance and at least one advertisement are selected based on previously collected caller information; and one or more information services coupled to the directory assistance service, wherein the directory assistance service uses the one or more information services to search for information about the unavailable number and the caller's number to provide additional information and advertising to the caller at the caller's number and one or more other alternative numbers associated with the caller's number from the one or more information sources external to the telephony network and one or more information sources internal to the telephony network.