Why does a customer call you to complain?
If a customer complains, it is because they want your attention. In many cases they want you to do better. Seth Godin writes a very short, pithy post about this here.
The complaining customer doesn't want to leave. They just want to be heard.
It is similar for the Referring Customer. If your referral program is passive and just provides for a free month of service, it will never work. People want to be recognized. They want a prize. (So do employees!).
"Try giving them a chance to be a voice of the concerned, energetic customer, a voice that needs to be heard by people who actually make decisions."