Trouble with IP address lookup

Hello everyone! I'm super new to this whole SaaS/web tools thing and just launched a very simple tool called 'What is My ISP?'. It's meant to help users quickly find their internet service provider based on their IP address.

I'm running into some frustrating accuracy issues, especially with getting reliable ISP data. I'm hoping some experienced folks here can point me in the right direction.

• The Core Problem: My tool relies on IP address lookup services to identify the ISP. While it works okay for major providers, I'm finding a lot of inaccuracies or generic results for smaller, local ISPs, or when users are on mobile data.
• What I've Tried So Far:
  • I started with some free IP geolocation databases (like MaxMind's GeoLite2).
  • Then I experimented with a few public APIs (e.g., IP-API, Abstract API) for real-time lookups.
• Where I'm Struggling:
  • Data Accuracy: Often, the reported ISP is a large backbone provider rather than the actual local provider the user pays for.
  • Coverage: Specific regions or smaller ISPs seem to be poorly covered.
  • Cost vs. Accuracy: The more accurate (and often real-time) services seem to jump quickly into paid tiers, which is tough for a beginner project with no revenue yet.
  • VPN/Proxy Detection: Sometimes it reports a VPN provider as the ISP, which isn't what I'm looking for.
• My Main Question: What are the best (and ideally, most affordable for a bootstrapped project) IP address lookup services, databases, or strategies you'd recommend for reliably identifying a user's actual Internet Service Provider? Are there specific industry secrets or lesser-known providers that offer better accuracy without breaking the bank?
• Thanks in advance for any help or guidance!