How do you solve customer complain ?

The Key to Solve Customer Complain is - Assuming that there is a robust Customer Complain Management Process already in place 

A. First do Quick Acknowledgment : Most Customers get dis-satisfied in delays by the organisations in Acknowledging the complaints

B. Second Understand and define the problem using functional experts of related area - by defining the complain half the issue is solved. More often than not we dont understand the complain and do not even verify with the Customer if this the problem

C. Fix a benchmark time limit to resolve the the Complain : Track it regularly and escalate the problem much before the target time of solving the problem

D. Implement the Solution and verify with the customer if the problem is solved to his satisfaction 

In all the above the Response time, Attitude, promptness and most importantly keeping the time and cost promise - are the most important dimensions