Abstract: A unique cellular telephone billing system (100) processes call detail records (102) of cellular telephone calls made by users of customers to produce invoices and reports containing consolidated billing, usage and cost information for the current and other eligible cellular service plans. Eligible cellular service plans are identified for each user in a candidate file and costs for accumulated usage data are calculated (216) under the current and eligible cellular service plans. The calculated costs for the current and eligible cellular service plans may then be compared to determine the most cost effective service plan for each user on the basis of peak and off-peak usage and customer discounts. Reports may be generated (218) for each user illustrating consolidated billing, usage and cost information by sorting on the basis of the corresponding key identification number and information format.