Creditors can come after you when you owe money, and they can ask you to pay. However, that does not mean they can harass you. This is illegal under the Fair Debt Collection Practices Act as addressed by the Consumer Financial Protection Bureau.
So, what is the difference between harassment and a simple request? One thing to consider is repetition. If they call you once and tell you what you owe, asking for payment, that's fine. If they call you three times a day, that's harassment.
Additionally, they have to tell you who they are when making those phone calls. Anonymous calls telling you to pay up are forbidden.
The tone of the phone calls should also be informative, not threatening. They can't tell you that you'll be physically harmed, abuse you with obscene language, or try to annoy you. Debt collectors are not supposed to pester you into a payment or attack you for a failure to pay.
Finally, though they can tell the credit reporting companies if you haven't paid, they cannot publish your personal information in public lists. This could be done as an attempt to shame you into paying, but it's illegal and is a violation of your privacy.
Even when collectors follow these regulations, it can still be frustrating to work with them, and you may feel like you're being harassed or pursued at every step. Be sure you know what options you have. One way to get rid of debt in Georgia, for example, is to declare Chapter 7 bankruptcy and start over with a clean financial slate.
Source: Consumer Financial Protection Bureau, "What is harassment by a debt collector?," accessed Aug. 23, 2016