Hello,
there is a quality system called COPC (Customer Operations Performance Center) that is based on performance measurement and improvement. It emphasizes quality, service and efficiency and it has been designed especially for the Customer Service industry. In the standard’s item 4.3 Performance Measurement you can find a list of metrics for all types of transactions/customer related processes and different types of services (inbound, fulfillment, technical support/help desk, outbound, e-commerce).
Have a look at http://www.copc.com/Library/public/ex.htm.