I can help make it forceful, but it's best to stick to claims you know are true. In particular, calling it a "scam" could be risky unless you have evidence they intentionally defrauded you. Here's a strongly worded version that focuses on your experience:
Absolutely unbelievable. We paid $570 for a private ice cream truck to celebrate our friend's graduation, and they never showed up. No truck. No explanation. No respect for our time, our money, or our friend's once-in-a-lifetime celebration. We spent the day scrambling to figure out what happened while our guests stood around waiting. They completely ruined one of the biggest attractions of the party and left us frustrated, embarrassed, and furious. Taking hundreds of dollars from customers and then failing to provide the service is beyond unacceptable. This company's complete lack of professionalism and accountability destroyed what should have been a fun, memorable day. Save yourself the disappointment and book literally anyone else. read more