It happens even to savvy consumers, including Consumers’ Checkbook staff: Sometimes—even after you do extensive homework before making a purchase or contracting for a service—things still go wrong. The supposedly repaired clothes washer is once again inoperative, and the repairperson says it’s a new problem (which, of course, it’s not). The TV starts acting screwy exactly one week after its warranty expires (of course). The crown falls out of your tooth after only four months of chewing (seems like it should outlast your caramel cravings by a few years).

Although most of us gripe about service headaches to family, friends, and co-workers, we seldom—studies show it’s as few as one out of four—complain to the company that dropped the ball. And many consumers who do complain to businesses do so ineffectively.

A lot of consumers remain silent because it seems like too much trouble to complain, or they want to avoid a confrontation. Others don’t complain because they think it won’t help—the warranty expired a week ago, so the store won’t do anything. But, in our experience, telling a company—especially a reputable company—that things didn’t go well often produces good results. The trick is to complain effectively, and to diligently follow up.

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The first step is to make sure the company’s owner or manager knows you are dissatisfied. Even if the employees you dealt with know you’re unhappy, that information might not reach someone who has the authority—and cares enough about customer service—to put things right.

If your gripe is with a large company—and its customer service team did not resolve it—obtain an email address or phone number for the company’s CEO or president. Although the company’s top executive is unlikely to handle your complaint personally, their staff is likely to give it to someone in the company who can help you—and is more likely to respond to a request that comes from the top.

If your complaint involves a product that you bought or was installed, contact the manufacturer. Even if your problem did not result from a manufacturing defect, the company may want to settle your claim rather than risk your ill will.

In your complaint, state the facts as you view them, why you feel entitled to relief, and how the company can make amends. Make your request reasonable. For example, don’t ask for a full refund on a home improvement project if four out of five tasks were performed correctly.

Complain in a firm but nonthreatening manner. No one responds well to hostility: If you are intemperate, an otherwise reasonable business owner might respond in kind—and what could have been a calm (and quick) resolution escalates into a feud. Even if you believe you were intentionally cheated, don’t utter words like “crook,” “criminal,” “incompetent,” or...you know...worse. Harsh words rarely get positive results.

If complaining in writing, provide copies of relevant documents such as contracts, invoices, receipts, and previous correspondence with your email or letter.

Another option is to post your complaint—and your desired resolution—on social media sites and tag the company. This forces the company to decide whether it wants to attract good or bad publicity from your dispute. While it’s not too risky to ignore complaints from one customer, many companies will respond to complaints broadcast to hundreds of other potential customers. Many companies, particularly national ones, have staff who monitor social media websites to resolve complaints quickly and show that the company is responsive to its customers.

Still no favorable resolution? Complain again. With large companies, ask that your case get “escalated” to the next manager on the corporate customer service food chain. Unfortunately, with some companies you might have to fight (politely!) through several layers of staff to reach a resolution. For example, I recently had to complain to increasingly higher-up staff at Alamo Rent a Car for nearly six months to get a refund for the $276 “special cleaning fee” it charged me to vacuum my kids’ crumbs from the backseat of a rental.

If the company won’t do the right thing, there are third-party programs that can help.

If you paid using a credit card, the federal Fair Credit Billing Act and the policies of credit card issuers provide enormous leverage by allowing you to withhold payment for goods and services you believe are defective or not delivered as promised. After you’ve tried unsuccessfully to resolve the matter with the service provider, contact your credit card bank to dispute the charge (you usually can do this even if you’ve already paid the bill). Once you’ve requested this “chargeback,” your credit card bank will place a hold on the disputed charge and investigate. The service provider can protest the chargeback, but sellers rarely successfully reverse chargebacks if the customer has returned (or tried to return) the goods or can document the service defect.

Another option is to file a complaint with a government consumer agency. Your most broad-reaching resource is the Massachusetts Office of Consumer Affairs and Business Regulation (888-283-3757), which has legal authority over many types of businesses. You can complain to this office even if you’re not sure it has jurisdiction over your complaint: It will refer matters it can’t handle to a local consumer protection agency, another state agency, or a federal agency. The matter might be resolved via phone or email, but the Office may also perform inspections, gather evidence from third parties, do legal or technical research, or mediate the dispute. The Office’s staff might do more than resolve your complaint; they might get the merchant to agree to change business practices and/or provide relief to additional aggrieved consumers: or they might force the business to pay penalties.

In addition to government consumer agencies, you can seek help from a private agency, such as the Better Business Bureau, or from the watchdog department of a local media outlet—for example, WBZ’s Call For Action (617-787-7070) or NBC10 Boston Responds (888-521-6397).

If you still can’t resolve your complaint, you may be able to bring an action in small claims court. Most courts have legal advisers to help you prepare your case.