From a WSJ article (no link available):
Sprint Nextel Corp. has taken the unusual step of disconnecting customers who call customer service excessively. The country's third-largest wireless provider, with more than 53 million subscribers, has sent letters to about 1,000 subscribers terminating their contracts, according to Roni Singleton, a company spokeswoman. "The number of inquiries you have made to us ... has led us to determine that we are unable to meet your current wireless needs."
This is a great idea. Fire your worst, most costly clients. It saves you time, resources and money. It's Pareto's Principle: 80/20 -- 80% of your complaints come from 20% of your clients.