Dear Neha,
In view of the facts brought out by you the question of taking a legal action or issue of a warning will not be purposeful without giving him an opportunity to explain his position. Further, the warning will not be effective once the employee is not responding to your calls. Accordingly, I suggest to please write a letter to the employee as under:
Name, father's name, address (of the employee)
(letter to be sent on his present and permanent address per regd post-a copy to be paced on the Notice Board)
You proceeded on two days' leave on -------dates and thereafter informed us (orally or what-pl specify) of having met with an accident and sought extension for which you have not sent a formal application, supported by medical certificate from the doctor concerned(to be atleast a Regd. Medical Officer) despite being required to do so by us time and again.
We will like to inform you that taking leave without prior approval/ permission of the competent authority ( as in your case) falls in the category of the misconduct as per the extant rules of the company as such, besides non payment of salary for the period under reference the management shall be well within the rights to take further action as per the rules of the company as may be applicable in your case.
In view of the above you are hereby directed to report for duty within ------------days(insert suitable number considering the distance involved) of the receipt of this letter. In case you fail to report for duty or submit a substantive proof with regard to your absence, the management will be obliged to take such action against you as it deems fit.
(---------------)
cc. department concerned