How do i handle an angry customer that is not ready to calm down?

BE PATIENT LISTEN TO HIM UNTIL THE END .TRY TO CONVINCE HIM AS MUCH AS YOU CAN.STILL IF HE IS NOT CALM  DOWN  GO TO YOUR SENIORS BRING IT TO HIM  AND TELL THE STORY INFRONT OF HIM SO THAT HE WILL UNDERSTAND  THAT THEY ARE TALKING ABOUT HIS PROBLEM TO  BE SOLVED.

just let him say everything on his mind I will listen to him calmly, once you give customers the chance to say every thing  they want they will reach to a point that they will be calm and willing to listen to what you have to say this way you can reach for a solution.  

i will tell him that he's on right and we will make up for his lost time and that we are here to fullfil all his needs