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The phone rings, and someone tells you that you need to repay an old department store bill – right now. Don’t panic: while calls from debt collectors can seem pretty scary, they are legally obligated to operate under a strict set of rules, and debt collectors usually want to work with you. Here are the key points to know.

The debt collector may not be the original creditor. Some large firms, like credit card companies, have their own collections department. Other times a business will hire a collections agency to try to collect debts it considers delinquent, which usually means anything over 90 days unpaid. There are also companies that buy delinquent debts for far less than they’re worth and then try to collect on them. “The third-party collectors are most often the ones that seem rough,” says David Jones, president of the Association of Independent Consumer Credit Counseling Agencies.

Read next: Which Debts Should I Pay Off First?

Debt collectors have lots of restrictions. Federal law prohibits collectors from engaging in what it considers abusive practices, which includes calling you very early (before 8am), very late (after 9pm), or at your place of work. They’re also not allowed to misrepresent the amount you owe, or threaten you with any kind of violence. For a complete list of protections, see the Federal Trade Commission's site. The debt collector also must send you a written notice of how much you owe within five days of initially contacting you. If you believe a debt collector has violated restrictions, immediately report him to the Consumer Financial Protection Bureau or Federal Trade Commission (you can submit a complaint online at consumerfinance.gov or ftc.gov).

You’ll benefit from saying less. Debt collectors are trying to assess your ability to pay and may try to get you to say things you shouldn’t by acting either friendly or intimidating. Either way, your best bet is to keep the conversation as short and businesslike as possible. Never give out financial information such as your bank account number over the phone, and if you aren’t sure that you owe the amount they say, ask for written proof. You can, however, negotiate with a collector; tell them how much you can afford to pay and ask if they will settle for that amount. If they accept, get confirmation of the deal in writing before you pay.