Medical debt affects many people’s lives. And repaying what you owe can get more complex and stressful when that debt gets sent to collections. On Sunday’s Last Week Tonight, host John Oliver tackled the issue of medical debt in an unexpected way.

“Clearly, if you have debts, you should pay them if you can,” he starts off in the segment. “But many people can find themselves in debt through no direct fault of their own.”

From here, Oliver delves into the practice of debt selling, in which companies purchase billions of dollars of debt from creditors, often for pennies on the dollar. According to the segment (which you can see in full on Credit.com), consumers’ information tied to the debt — such as their name, address and Social Security number — often passes through several hands without being verified.

As a result, consumers can find themselves being sued for debt they don’t recognize, out-of-statute debt (“debt that’s so old you can no longer be sued for it,” Oliver notes), debt that they’d already paid off or debt they took care of in bankruptcy. This type of debt is often called “zombie debt”, or old debt thought to be settled and buried.

Once a company has purchased the debt, they’ll typically try to collect it themselves or hire a debt collector to help. Many collectors work in the bounds of the law, Oliver says, but sometimes, illegal tactics, such as leaving threatening voicemails, are utilized to get consumers to repay.

The debt-buyers’ trade group, DBA International, told Oliver the industry is working to regulate itself. (It did not respond immediately to Credit.com’s request for follow-up comment.)

The barrier to entry into the debt collection business is low, Oliver says. To illustrate this point, in April, Oliver’s team spent $50 to incorporate a debt acquisition company online in Mississippi. He named it Central Asset Recovery Professionals. Soon, the company was offered a portfolio of nearly $15 million of medical debt from Texas at a cost of less than $60,000. For that amount, CARP would receive the names, addresses and Social Security numbers of nearly 9,000 people.

Following the purchase, Oliver could have easily had employees start calling people, “turning their lives upside down over medical debt they did not have to pay,” he said. But instead, at the end of the segment, he decides to give it away.

Dealing with debt

Those whose debt was purchased by Oliver could be considered lucky, but many people aren’t when it comes to paying back certain bills. If you’re dealing with medical debt, it’s important to remember to review your credit reports annually and check your credit scores on a regular basis to see how it may be affecting your credit. (You can view two of your credit scores, updated each month, for free on Credit.com.)

And, if you are dealing with debt collectors, it can help to know your rights. You can find a crash course on debt collection here.

This article originally appeared on Credit.com.