If you feel the situation is beyond your ability to deal with, call for assistance from your supervisor. When your supervisor arrives, paraphrase the customer’s problems so the customer is made aware that you were paying attention. It also avoids the customer becoming upset again by having to repeat the problem.
Remember taking the appropriate action can only be done after hearing the problem, understanding the customer’s feelings and combining it with a sincere apology.
It is important to thank the customer. While it may sound odd, thank the customer for bringing it to their attention. Many people may be too proud or do not want to inconvenience the person who is assisting them. When thanking your customer for bringing it to your attention, they are giving you an opportunity to fix the issue.