How do I ask for the manager without sounding like a complaint?

Ask about the order, not about the person: Could I speak to the manager, please? It's about the order, not about you. Then give the five facts in order and stop. Managers hear complaints all evening; a short factual summary is the unusual version that gets a decision.

If the manager is not in the room, ask when they will be: When would the manager be back? Then choose: wait, or put the facts somewhere written down. A short email or a message through the restaurant's contact form, with the date, the time, the table, the order, what went wrong and what you want, is read by someone who was not there, so it has to carry the facts alone. Keep the receipt: it holds the time, the table and the items, and it is the one part of the evening neither of you has to remember.

How to Order Food in English When the Wrong Dish Arrives: Fixing a Restaurant Order →