The FDCPA says debt collectors can’t harass, oppress, or abuse you or anyone else they contact. Some examples of harassment are:
Repetitious phone calls intended to annoy, abuse, or harass any person answering the phone
Obscene or profane language
Threats of violence or harm
Publishing lists of people who refuse to pay their debts (this does not include reporting information to a credit reporting company)
Calling you without telling you who they are