Wrong rates, rates applied improperly, estimated meter readings, meter malfunctions, meters improperly installed, billing for meters that do not exist, billing for accounts that belong to others, wrong type or size of light, riders not applied properly, calculation errors, double billings, double payments, charges not allowed in the contract, contracts with erroneous terms, and tariff violations. We check all historical billing data available and also perform field checks on certain meters and facilities.