So there are at least two violations: not sending the original contact letter and refusing to verify your alleged debt. There may be others, such as not being licensed or the tone of the attorney on the phone with you. If you sue and the agency settles, you can get $1,000 statutory damages. Some attorneys deduct the $350 filing fee from this award, so ask about that.
Yes, as Mr. Grafton noted, "lawyers" are excluded from the definition of “collection agency” by operation of Minn. Stat. § 332.32(a), so collection law firms, such as Messerli & Kramer in Minnesota, are exempt from licensure.