At any reasonable time, the commissioner may examine the books and records of every registrant and of any person engaged in the business of providing debt management services as defined in section 332A.02. The commissioner once during any calendar year may require the submission of an audit prepared by a certified public accountant of the books and records of each registrant. If the registrant has, within one year previous to the commissioner’s demand, had an audit prepared for some other purpose, this audit may be submitted to satisfy the requirement of this section. The commissioner may investigate any complaint concerning violations of this chapter and may require the attendance and sworn testimony of witnesses and the production of documents.