Dear Sangeeta Bala,
You can solve the aforementioned problem as follows:
1) If the employee is not in a managerial cadre, as they are not reporting for duty and are sending an SMS, ask them to submit a resignation letter. If they submit the resignation letter, waive the notice period, accept the resignation, prepare their full and final settlement, and send it to their residential address for acceptance.
2) If the employee is in a managerial cadre, act according to the terms of the contract (i.e., appointment letter).
3) In the case of an employee who falls under the definition of a worker/employee as per the Industrial Model Standing Orders Act, 1946, you must follow the principles of natural justice. This involves issuing a show-cause notice, then a charge-sheet, conducting a domestic inquiry (if the employee does not respond to the inquiry), then conducting an ex-parte hearing, and finally terminating their service as per due process of law.
Regards,
N. K. Jagtap