Remember when you were courting someone you cared about? You did crazy little things like sending them notes with candy, calling them to ask if everything is going fine, and keeping your commitments when you made a promise. Are you with me? This is the role of customer service. They are charged with the care and feeding of relationships for the long term.
You may say that this is the role of your Sales organization. No customer can question the sincerity of the customer service organization that sends out love notes and gifts to customers. The Customer service department has no self-interest in a commission so this kind of care and feeding comes across pure and sincere. Have you considered sending a small gift along with a customer survey indicating to your customer that you care about them and would like them to take some time and provide some feedback?
Here is a great White Paper on Customer Service Best Practices-What Features and Functions to look for in Customer Service Software.