1. A telephone-based commerce system for conducting sales transactions involving a selected group of products or services which are advertised for sale at a particular telephone number, said system comprising: a voice portal which is assigned the particular telephone number for receiving incoming telephone calls; a computer coupled to a memory and having circuitry for selectively communicating with a payment engine which provides pre-enrollment services and with an order fulfillment facility; and a voice recognition system communicating with said voice portal and said computer for converting voice signals received from a caller to digital signals which are supplied to said computer, and for converting digital signals received from said computer to voice signals which are transmitted via said voice portal to the caller; wherein said computer is programmed, in response to said system receiving an incoming telephone call, to: (a) provide digital signals to said voice recognition system, in response to which said voice recognition system generates voice signals to said user either (i) offer the caller a single product or service associated with such telephone number; or (ii) prompt such caller to select from a limited selection of goods or services associated with such telephone number; (b) provide digital signals to said voice recognition system, in response to which said voice recognition system generates voice signals to said user which provide the caller with product and price information associated with an offered product or service; (c) provide digital signals to said voice recognition system, in response to which said voice recognition system generates voice signals to said user which prompt such caller to provide identification information; (d) in response to receiving digital signals from said voice recognition system corresponding to the voice selection by said caller of one or more goods or services, determining from data stored in a memory account information concerning such caller, including whether such caller has pre-enrolled in a payment processor; (e) provide digital signals to said voice recognition system, in response to which said voice recognition system generates voice signals to said user which prompt the caller to elect either to pay through a pre-enrolled payment processor or to pay through an alternate method; (f)(i) in the case of a caller who elects to pay using the pre-enrolled payment processor, provide digital signals to said voice recognition system, in response to which said voice recognition system generates voice signals to said user which prompt the caller to provide security verification; (ii) in the case of a caller who is not pre-enrolled in a payment processor, or elects to pay through an alternative method, provide digital signals to said voice recognition system, in response to which said voice recognition system generates voice signals to said user which prompt the caller to supply payment information and security verification; (g) transmit to a payment engine transaction payment information and security verification for a transaction approval; and (h) upon receiving a transaction approval from said payment engine, transmit digital signals to an order fulfillment facility to fill such order, wherein such system permits a user to select and purchase selected goods or services from any a telephone without the participation of human salespersons.