It was a full toss ball of Harshit Rana which seemed like no ball over the waist but when field umpire refer the decision to third umpire , Micheal Gough made his design by adjusting the ball and waist height of Kohli and gave out.
This decision was given by referring the law of ICC law rule

Why Virat Kohli got angry & did he abused umpires?

In today’s match played between KKR vs RCB in Eden Garden while chasing the target of 223 Kohli came to open the inning and was playing flawless but a on a ball of Harshit Rana he was given out by third umpire. Virat Kohli lost his temper and argued with umpire while going back to the dug-out.
This decision makes him upset and he had to depart toward pavilion on the score of 18 run of 7 balls. Before departing he argued with umpire and slummed the bat on the ropes of boundaries and he did not abused umpires and keeps the cricket as gentleman game.

What is the ICC no ball rules for over - waist condition?

According to Law 41.7.1 of the ICC Playing Conditions, “Any delivery, which passes or would have passed, without pitching, above waist height of the striker standing upright at the popping crease, is to be deemed to be unfair, whether or not it is likely to inflict physical injury on the striker. If the bowler bowls such a delivery, the umpire shall immediately call and signal No ball.”