If you have ever been put on hold indefinitely, or if you have waited in vain for a promised rebate, or if someone gave you a bad time when you tried to return a defective product, take heart. A quiet revolution is just getting underway in the customer service departments.

Customer service has always been spotty. Often, all you get is a “Have a great day,” and that’s it. On the other hand, some companies, say, L.L. Bean or Bose Radio, answer right away, do what you ask, and produce another satisfied customer.

To be sure, some customers abuse an accommodating system. An L.L. Bean customer once asked a night clerk, “If I returned a worn-out old jacket that I bought here 25 years ago, would you give me a new one?” The clerk, without missing a beat, replied, “Of course we would.” (pause) “But if we did, what would you think of yourself?”

Other customer scams include returning a digital camera after using it to photograph a family vacation or wedding. Also, waiting for a sale, returning an item bought earlier and buying it again at the sale price.

J.D. Power and Associates issues an annual rating of customer service at cell phone companies. T-Mobile and Verizon Wireless currently lead the pack. Cingular, which has undergone a storm of complaints, is jacking up its department and setting up a special training school for call center operators. Since cell phones are a “mature market,” with so many people owning them, more than half of the users switch companies each year. Good customer service can help hold them.

Consumer Reports rates products in part by their customer service. Some it calls excellent, others merely adequate, inadequate, “a mixed bag” or very poor. It advises companies how to make their sales rooms and Internet sites attractive and easy to use, with customer service numbers in plain sight.

For the consumer, the current issue of the magazine has good advice, for example, for a passenger whose plane service has gone sour and stranded him away from home. Insist on another flight. Demand a hotel room, or at least the air line hotel rate. When you finally get home, fire off a letter to the consumer-affairs director with all the details.

If a product doesn’t work the way the clerk said it would, try claiming there was an “implied warranty.”

The Consumer Reports headline sums it up: “The New Art of Complaining: How to take your complaints to the next level and get fast results.” One more necessary skill to master.