Six months back, I paid Rs. 140 (Rs. 25 for the new SIM and Rs. 110 talktime) for an existing Airtel number. The new SIM got activated in 15-20 mins and the talktime was added too.
On Tuesday, I paid Rs. 125 (Rs. 25, I guess for the new SIM and I was promised Rs. 85 talktime and not Rs. 50 like ganeshran mentioned). It took more than 6 hours for the old SIM to get deactivated. I only checked the next morning). SMS wasn't activated till last night. And I'm yet to get the talktime credited. Only then will I know if I'll get Rs. 85 or Rs. 50.
I'm not sure why there's this difference in service in 6 months. I was told that TRAI has to check our application and activate or something. The more years pass, the more things get difficult in India. What a country!