QUESTION: How do you handle angry or upset customers over the phone, and what techniques have you found to be effective in de-escalating situations?

Best way to handle angry customer is active listening. Be polite and let the client finsh the conversation first, do not interfere in between. Clearly understand the problem, repeat  to the customer about the case to make sure what exactly he/she needs. Then analyse and provide the possible solutions in a polite way.

Customer  angry situation .customer talking usefully 

First we lisen silently what,s saying costumer and analise issues after then slowly convence to costumer to solve his issues.

 You must make him feel that you Are standing with him not opposite, and try to control your feeling and make him rekax by saying yes you Are right but we have a suitable solution for your case we are here to solve your problem 

The techniques I used was 

Listening 

Calming the customer 

Answering their questions 

basic way to handle and angry customer is just to stay calm and Listening what they're saying and then resolve the situation by satisfying the customer