Please analyze the tweet "Incredibly shocked and disappointed with @united customer service. Really making me rethink flying with them in the future. #unhappy" and classify its emotional content. Choose from the following emotions: anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust. If no emotions are detected, respond with "neutral or no emotion".
anger, disgust, pessimism, sadness