Our app was Free App of the Day on amazon four years ago, which was a horrible mistake for many reasons, but the people who received the app that day and have emailed us are just the worst set of people I have ever encountered.

Absolutely true in my experience. We had a service with free and paid tiers. The paid customers were uniformly respectful and even helpful. The free users were usually demanding, sometimes abusive, and would spend hours trying to convince you that they can't survive without your service but they also shouldn't have to pay for it.

We don't have a free tier, and we get a funny support request more often than I would have thought: people who don't want to cancel their account, but don't want to pay anymore. I wonder how often this actually works.

I would be terribly tempted to counteroffer with a special plan where we disable their account but keep billing them at twice the rate.

I called to cancel my cell phone service and the carrier offered me half off. I was cancelling because I found out a competitor was half the price. (This is in the US where cell phone bills are unreasonable even at half price) It was so infuriating to learn that I was overpaying for months and months. I still cancelled.

Every year when the previous year's promotions expire, I cancel my TV and lower my internet down to something cheaper. Every time, within 10 business days I'll get a call for a better offer.

That usually works with internet and probably cable TV as well. Really any of the "utilities" that aren't actually regulated by a PUC.