What constitutes harassment by an auto loan company?

The Fair Debt Collection Practices Act (FDCPA) is a federal law that spells out exactly what debt collectors can and cannot do. Unfortunately, the FDCPA doesn't necessarily protect you from the creditor themselves, but only a collector. Some states have set standards and made laws above and beyond the FDCPA that essentially make the same rules apply to creditors as well. Your state attorney generals office or consumer protection agency could give you more info. You can also check out the Fair Trade Commission website. They enforce federal collections laws. Research your bank online and see if they have had any other complaints about their collections practices. In a nutshell though, they cannot threaten you or harass you. You could always send them a cease and desist order telling them not to call you anymore, however you may have to find some common ground if you want to keep your car.