Airtel - Unwanted calls

I have been getting calls from Airtel since *-* months for porting my number to Airtel. I had made it clear on the very first call that I am not interested in Airtel as I had very bad experience in the past with Airtel. The executive tried convincing me but I was very adamant in not using Airtel. I had asked them to mark my number to the DND list. But Alas! I kept receiving calls. I talked to somebody calling himself a Manager ( Deepak I suppose) and he assured me that I wont be receiving any calls from Airtel hence forth. As usual false promises I kept getting calls from Airtel.

Today ( *nd August ****) I got a call from a female executive from Airtel, I was so frustrated with the call that I asked her to connect me to the manager for which she answered "Ma'am kya aapko port karna hai?" I said no Connect me to your manager for which she said "Ma'am kya aapko plan k baare me pata karna hai?" I asked her which language she understand, she just transfered the call to some other female without saying anything. Now this female opened the call with I am calling from Airtel, I asked her whether she is the manager for which she said no. I asked her to connect the call to the Manager for which she said I cannot connect to the Manager and disconnected the call abruptly.

This was exacty the reason behind me not liking Airtel because they have got a pathetic customer care agents and pathetic after sales service.
I have been requesting them to put my number on DND which is not done yet.

Worst Customer Care service provider.