Monthly Billing Details Analysis

I'm looking for a detailed comparison report of my invoices' billing details across multiple Excel files, focusing on product prices.

Key Requirements:
- Compare current charges with last month's charges
- Categorize charges into relevant charge categories
- Present findings in a clear, comprehensive table.

Ideal Skills:
- Proficient in Excel
- Excellent data analysis skills
- Detail-oriented
- Ability to present data in a clear, comprehensible manner.

Include bar charts and pie charts to represent the data visually. Please analyze billing details for the last 6 months.