Apart from Tamil Nadu, other circles that have the Combo 18 plan include Chattisgarh, Chandigarh, Chennai, Daman and Diu, Dadra and Nagar Haveli, Gujarat, Goa, Haryana, and many more.

source https://gadgets.ndtv.com/telecom/news/bsnl-combo-18-plan-tamil-nadu-circle-launched-1-8gb-daily-data-two-days-validity-2232094