There is a tendency when first starting service level management to focus in on the response performance. It is easy to make the numbers look good. All you have to do is close a case within the time specified without doing anything. While this makes the numbers look good, in the end you will have customers upset. Customers do not really care about the numbers. They only want their issues taken care of to their satisfaction.
Customer Satisfaction Surveys are one way to provide checks and balances to the empirical numbers of SLA compliance reports. Another way to make sure customers are taken care of is to have a policy for re-opening a case if the customer calls in to say they are dissatisfied. You should then have a report that shows re-opened cases. Management should use this for continued training.
Here is an example of a good Customer Satisfaction Survey Report:
Here is a great White Paper on Implementing Service Level Agreements. See https://www.givainc.com/wp/it-help-desk-software-cloud-whitepapers.cfm