Bad checks are generally a matter of state law. A federal criminal warrant would not be issued for a violation of state law.
In most states, writing a bad check is a crime only when there is an intent to defraud the creditor; otherwise, it will only constitute a civil violation.
Merely defaulting on a debt is not considered a crime for which a person would be arrested for. This country did away with debtors' prisons long ago.
Debt collection agencies use a multitude of methods to "encourage" debtors to pay their debts. There is a point, however, when this "encouragement" turns into unwarranted threats and harrassment. The agencies will try to scare people into paying back the debts with the use of false and deceptive practices.
In 1978, Congress passed the Fair Debt Collection Practices Act (FDCPA). The FDCPA governs how far debt collection agencies can go in collecting debts. If a debt collection agency violates a provision of the act, they may be required by law to cease their activities and/or pay damages to the debtor.
Disclaimer: Nothing in this answer should be construed as legal advice, nor as creating an attorney-client relatioship. This answer is provided for informational purposes only.