If you're unhappy with the meal, tell your server right away
Don't wait until you've already eaten your entire meal to tell your server that you hate it. If you're really unsatisfied after one or two bites, there's still a chance you can send it back and order something that's more to your liking. Also, don't blame them if you didn't like what you ordered! They're not the ones preparing the food, and if they at least brought you the correct dish, they've done their job.