Errm... isn't this is how Truecaller works? I use it. Drop it - it's been done already.

I was in a very similar position to you. (Asp.Net with C#). After some research, for the front-end I chose Typescript (if you squint really hard it looks a bit like C#) as the base language. The as a FE framework (believe-me that you will need one unless you're a masochist), I went with Svelte. I chose Svelte over React because my stuff runs on a mobile, so download size is important. Watch I built the same app 10 times // Which JS Framework is best? - YouTube[^] for a nice overview of the main FE frameworks out there. I'm as yet undecided on a back-end. There's nothing wrong with a Microsoft back-end, unless you're paying for it. Just my $0.02.