First the bad news: A debt collector can call, text or write you to request payment for a debt you owe. The good news: There are limits to what a collector can do when talking to you. The Fair Debt Collection Practices Act prohibits collection agencies from being abusive, harassing or deceptive when collecting on a loan.So, how do you know when a debt collector's behavior has crossed the line? Prepare yourself before answering your next collection call by knowing your rights. [See: 12 Habits to Help You Take Control of Your Credit.]You can confirm that the debt is yours. Take a deep breath, gather your thoughts and verify that the debt collector has dialed the right person. "Consumers have the right to ask questions and get more information," says April Kuehnhoff, staff attorney at the National Consumer Law Center in Boston. "I try to counsel people to slow down and feel like they can take the time that they need to discover whether this really is the debt that they owe."If you can't confirm that the debt is yours over the phone, then get the details in writing. Within five days of first contacting you, a debt collector must send you a "validation notice" in writing outlining what you owe, the name of the creditor and how to proceed if you don't think you owe the money.If you reply with a letter stating you don't owe the money or asking for verification, which you must do within 30 days of receiving the validation notice, the collector must stop contacting you (unless there's an update, such as legal action initiated by the collector or the collector sends written verification of the debt). The Consumer Financial Protection Bureau offers a range of sample letters for different situations when dealing with debt collectors. Of course, stopping contact doesn't erase the debt (if it's a real debt), and the collection company may choose to pursue legal action or report your debt to the credit bureaus.There are things that a debt collector can't do. Certain actions are off-limits to debt collectors, no matter how much money they're recouping from you. "The most important thing is to be wary," says Cara O'Neill, bankruptcy, credit and debt editor for Nolo, a publisher of do-it-yourself legal books and other legal information. An overly aggressive debt collector may simply be poorly trained or unprofessional – or he might be a scam artist. Legitimate collectors can't, by law:Harass you. A debt collector can't swear at you, threaten to beat you up or disclose your debts on a public list to shame you.Lie to you. A debt collector can't pretend to be someone he's not – such as an attorney, credit-reporting company employee or police officer. The caller can't claim that you've committed a crime, lie about what you owe or tell you that papers are legal forms when they're not (or vice versa).Threaten to arrest or deport you. A debt collector can't say he'll take actions that he doesn't have the power to take. "A legitimate debt collector will not be making those threats," Kuehnhoff says. The caller also can't threaten to take your property, unless he can do so legally. Discuss your debt with others. A debt collector can't call your mom, dad, friends, boss or anyone else (except an attorney in certain situations) to discuss the details of your debt.Call at certain times or places. A debt collector can't call you before 8 a.m. or after 9 p.m. unless you agree to it. The collector also can't call you at work if you're not permitted to accept outside calls during the workday.Misapply payments. A debt collector can't apply a payment to a debt you think you don't owe. He also can't deposit a post-dated check early. [See: 10 Ways to Protect Yourself From Online Fraud.]But they can do a few things that may surprise you. A debt collector may contact the people in your life to learn your home address, phone number and where you work. Debt collectors can contact you by email, phone, letter or text message to collect on a loan. The company they represent can report unpaid debts to a credit-reporting bureau – and potentially ding your credit score.[See: 10 Easy Ways to Pay Off Debt.]How to handle a misbehaving collector. If a debt collector is clearly crossing the line of legality, "that should be a red flag for the consumer to slow down, ask more questions, make sure that this is a legitimate entity," Kuehnhoff says.Keep a call log to track abusive or harassing collector behavior, experts say. Keep a pen and paper next to the phone and jot down the time of call, who called and what he or she said, Kuehnhoff says. Keep copies of any letters sent or received when communicating with the debt collection company. You may be able to take this information to a consumer attorney. And you can certainly report your experience in a complaint to the Consumer Financial Protection Bureau. Never give out important personal information such as your Social Security number, credit card number or banking information to get a harassing collector off your back, experts say. Ask for additional information on the loan, including who the original creditor is – since it may jog your memory – and what information they have about you on file, before making any payments. And know your rights, so that you're not harassed, bullied or intimidated into paying a debt you don't truly owe. 25 Was to Fix Your Finances Fast.