[header] How to handle an irate customer on the phone [title] Do not react. [step] Keeping calm is key; reactions such as anxiousness or anger--while natural--will make things worse. If the customer views you as calm and professional, the customer will tend to " mirror " your reaction. 
[substeps] Try focusing on your breathing, by taking deep, calm breaths. Do not be obvious about breathing heavily, however--it may come across as creepy or sighing.