CDL Hazmat is directed by the federal government. The customer service phone number is (833) 848-4759 and the application phone number is (855) 347-8371. In addition, please see the links provided regarding a HAZMAT Endorsement:
TN: https://www.tn.gov/safety/driver-services/commercial-driver-license/hazmat.html
TSA: https://www.tsa.gov/for-industry/hazmat-endorsement