Struggling to get accurate ISP from user's IP address?

Hey everyone! I just launched a small web tool called 'What is My ISP?' which is designed to help users quickly find out their internet service provider. It's a pretty basic tool right now, and I'm really trying to improve the accuracy of the information it displays.

I'm running into some frustrating inconsistencies when trying to accurately identify the Internet Service Provider (ISP) from a user's IP address. I've experimented with a few free IP geolocation APIs, but the results vary wildly between them. Sometimes they return generic data centers like AWS or Google Cloud, instead of the actual end-user ISP that the user is connected through. As a complete beginner in this area, it's quite confusing to sort out.

Here’s a simplified example of the inconsistent output I'm seeing for the same hypothetical IP address:

// Example lookup for a hypothetical IP: 203.0.113.42

API_A Result: { "isp": "Generic Cloud Provider Inc.", "country": "US" }
API_B Result: { "isp": "Local Fiber Network Co.", "country": "US" }
API_C Result: { "isp": "ISP Proxy Service", "country": "US" }

What are the most reliable methods or services, especially for a beginner like me, to accurately map an IP address to its true Internet Service Provider?