Pro tip: Stop giving hourly rates for project work, it's costing you money

I keep seeing freelancers in our field quote an hourly rate for a full project, like saying 'my rate is $75 an hour' when asked for a project price. This is a huge mistake. I learned this the hard way last month when a client agreed to my $75 rate for a website build, then nickel and dimed every single email and phone call, demanding I log exactly 15 minutes for each. The project scope ballooned but the client expected it to fit the original 'hours' estimate. Now I only give a flat project fee after a detailed scope call. It sets clear boundaries from the start and protects you from scope creep. The client gets a fixed cost, and you get paid for the value delivered, not just the time spent. Has anyone else switched to flat rates and found a good way to explain it to clients who are used to hourly?