A federal law known as the Fair Debt Collection Practices Act limits what debt collectors can do to harass you about debts.  In most states, like Missouri, the state laws do not provide much protection against harassment.  However, the federal law applies to all debt collectors, including attorneys.

The law applies only to "debt collectors." This means that the person calling you is collecting the debt that you owe to someone else. If the XYZ Company calls you directly to collect their debt, the Fair Debt Collection Practices Act does not apply to them. However, if the XYZ Company hires a debt collection agency to collect the debts, the law does apply to the debt collection agency.