A data management method and system to more correctly bill a customer of a reseller of telephone service, based on wholesale billing data of a telephone company. The wholesale billing data is divided into many very small parts, or cells, of information. The system accesses one cell of information at a time, and excludes a portion of the accessed information from subsequent data manipulation. Then, the system transforms the un-excluded information from one data format to another data format. The wholesale billing data can be in EBCDIC data format and the tabulated data is not in the EBCDIC data format. The tabulated data can be in a personal-computer data format. After transformation, the system generates tabulated data from the un-excluded wholesale billing data based on at least a user-preference. The tabulated data is then compared to the reseller's internally generated billing information to correct mistakes in the bills to the customer.