[Resolved]  Airtel Service — surrender of sim

I am an airtel customer for 4 years now. Couple of years in karnataka and past 8 months in MP. I surrendered my karnataka sim in the month of august '08 and took up new post paid connection in MP. Now i am required to surrender the sim in MP as i have moved out of india. my family member when tried surrender the sim, are asked for the photo id proof. i want to know y is an id required for surrendering? and to my surprise, the sim that i had personally surrendered at airtel office, has been receiving bill till the latest month. Then what is the meaning of the surrendering of the sim?? I really dont know what is airtel upto? inspite of being a regular & sincere customer, is this what we get back??