I receive monthly CDR spreadsheets from my carrier in Excel format and need a reliable way to spot billing discrepancies quickly. You’ll work with those Excel files only—no third-party feeds or call-quality metrics—to calculate what each call should cost based on my rating rules (rates per destination, minimum increments, free-minute blocks, etc.) and then compare that figure with the carrier-billed amount. What I need from you: a repeatable solution—Excel VBA, Python (pandas), or another local tool—that ingests a fresh carrier CDR, applies the rating logic, and produces two outputs: • A concise summary showing total minutes, expected spend, carrier-billed spend, and variance. • A detailed line-by-line sheet listing every call where the billed charge exceeds an acceptable tolerance, so my finance team can dispute specific items. Acceptance criteria - Runs on a new .xlsx file with no manual prep. - Flags all over-billed calls accurately according to the rules we agree on. - Code and formulas are clearly documented, with a short user guide. I’ll provide a sample month’s CDR and the pricing table once we start. Let me know which language or method you prefer and any clarification you need on the rating rules.