When I worked at Teleperformance back in 2007, i got my very first upset customer. My advise to you would be, learn to take control of the call. By that I mean, do not show nervousness in your tone of voice. It's all about tone of voice, if the customer is adament about being nasty, then you escalate it to your supervisor. Under no circumstance, is the customer allowed to abuse the Customer service reps. After you being totally nice to the customer, and they are still being rude, mean and nasty then raise your hand and get your supervisor to step in. I had to literally be counselled on how to control my calls with nasty customers, cause i had one like yours and freaked out about not being able to handle the call. Just remember you're in charge, not them. But, do NOT EVER be nasty back to them, you can and will lose your job. Always get the supervisor to take over the call, when they refuse to work with you. The customer needs to understand the Reps are there to help, as best they can help.