Airtel — About repeated and harassing calls of Airtel DTH

I am getting repeated calls from airtel dth for offers and asking me about why I am not recharging my setup box. They are continuosly calling from different different numbers many times a day since 4-5 months. I am really tired of telling the same reason to every call.
My father’s friend took my number just to recharge his setup box now he is no more and they have moved someplace else. Now we don’t have any contact with them.
Now I will lodge an FIR or will go in consumer court against airtel. I have recorded all the calls telling them to stop calling me by explaining the same reason to everyone.