Handling a complaint
A complaint is a regulated event from the moment it is expressed, whether or not the word is used.
Recognise one
Any expression of dissatisfaction about a product or service, including in passing and including when the customer says "I'm not complaining, but". Log it.
Acknowledge properly
Acknowledge the specific thing they are unhappy about, in their words. A generic acknowledgement reads as a form letter and escalates the complaint by itself. State the timescale that applies and who now owns it.
Classify
Root cause · product · whether it alleges financial loss · whether it alleges distress · whether it is a repeat from the same customer.
Escalate immediately
Vulnerability indicators, an allegation of fraud or discrimination, a threat of publicity or legal action, or a repeat complaint on the same issue.
Never
Defend, explain why the customer is mistaken, offer redress, or apologise in terms that admit liability. Say what will happen and by when.