The correct service to use in this case is AWS Cost Explorer because it allows users to create detailed and customizable reports that include both historical and forecasted data regarding cloud expenses. It can help the financial team understand future costs associated with new and existing cloud resources. While AWS Budgets assists in setting budget thresholds and alerts, it doesn't offer predictive reporting features. AWS Cost and Usage Report delivers comprehensive usage and cost data but lacks forecasting capabilities. Lastly, the AWS Pricing Calculator is designed to estimate costs prior to committing to services and does not produce past usage reports or future spend predictions.