If you've ever shipped a paid app, then you would know this problem. People use your app for weeks or months, then request a refund or a chargeback. This service exists to help developers state their case. And the reason I developed it is because of this update from Google: https://support.google.com/googleplay/android-developer/answ...
Apple and Google literally have APIs for developers to provide evidence (This is what RefundHalt does for developers), but like 95% of developers don't have a server to intercept these notifications and respond in time. RefundHalt does not automatically stop a refund. Apple and Google decide that; it only provides the evidence.
And yes, services like this already exist. RevenueCat responds to Apple's consumption requests for its users; Adapty has Refund Saver, there are a lot of services like this for Stripe as well.