Two elements of your question actually seem unfair: first, it is unfair to hang up on a customer; second, it is unfair that you were not provided with adequate training to prevent or deal with this type of situation.
Either way, there are some points to keep in mind when dealing with irate customers. Most importantly, listen carefully and actively to what the customers are saying. Be calm and respectful and avoid interrupting, and try to keep a caring and concerned tone in your voice. Sometimes customers want and need to vent, and once they do so and sense that they have truly been heard, things can calm down quickly.
Honesty, understanding, and empathy go a long way here. Let the customer sense that you are interested, involved, concerned, and passionate about solving the problem. You should ask questions, avoid being defensive, and give the customers a clear idea of the actions you are going to take right now to help them.
If you take these steps and still have difficulties with a difficult customer, the procedure should be for you to politely transfer the call to your supervisor. If you hang up on customers, you are not likely to hang around at the company.
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