What's the best way to do an ISP lookup for users?

hey everyone, really new to this whole SaaS thing, so please be gentle! i just launched a simple web tool, 'What is My ISP? - Find Your Internet Service Provider', to help people quickly figure out who their internet service provider is. it's basically an ip geolocation tool, pretty straightforward.

the thing is my current method for doing the actual ISP lookup is a bit... amateurish i guess? and it's not very accurate sometimes, which is a real bummer. often, it just gives generic datacenter info instead of the actual user's residential ISP, which isn't super helpful for my users.

i've tried a few things already, trying to get this right:

• i started with some basic ip-to-asn lookups, thinking that would be enough.
• then i moved on to trying a couple of free ip geolocation APIs i found floating around on github. they seemed okay for a bit when i was just testing with my own IP.

but the struggle is real. these free APIs either have really strict rate limits (which i hit superfast once a few people started using the tool) or the data isn't always fresh. sometimes they just fail completely, returning nothing, which is obviously not great for user experience. i'm also seeing a lot of users whose ISPs are misidentified, like, it'll say "google cloud" when they're clearly on spectrum or verizon. it's a bit frustrating.

so, for a tool like mine, what's the most reliable and efficient way to perform an ISP lookup? are there specific services, paid or otherwise, or techniques that you pros use to get really accurate and fresh ip geolocation data for internet service providers? i'm open to anything that can improve accuracy and reliability for my users.