In 2005
I had airtel internet connection, and had a normal modem. I was told that ADSL modem is better, and I called the customer care at 11 PM for ADSL modem. Next day morning by 11 AM, I got ADSL modem.
Once I returned from my home town at around 1 PM. When I came home, I realized that, both airtel phone and internet connection are not working. The reason that I came to know later was, the wires were cut, and they had to get new wires and set it up. By 3.30 PM, both phone and internet connection were working. Within 2.5 hours, they came to my house, found that, the wires were cut, they returned to office and brought wires to my house, and arranged everything. For a home connection, by any standard, it was too fast.
In 2010
If you have not bashed the customer care already from the number that you have, or if your profile looks like you are a normal person, then by default, airtel activates many services for you. For any service, the minimum charge is Re.1 per day, and if they activate three services, you will be paying Rs.90 per month. If you call the customer care, they would say that, you have accepted the service when you received the call. If you say that, you did not get any call, they just do not listen.
Recently, I took a new airtel number. After some time, I saw a message on my cell. It is not an SMS. It is like a message that is displayed after the call is ended to display the balance and expiry date etc. It said some thing like, "blah blah blah..To activate this service, click ok. To do not activate this service, click back". If anyone does not read that message or does not understand the message, they would click only ok. That is the acceptance of activating the service, and they would just activate it.
You cannot call karnataka customer care from outside karnataka. You can call only from karnataka number. If you are outside, and if your karnataka number is not working, you have no way of getting help unless you goto karnataka or you take help of people in karnataka (except airtel customer care people). If your number is AP's number, then you just cannot call customer care from outside AP, even from working AP's number.
Around a month back, I got message that, I have to submit id and address proofs. I submitted within a week, and I was still getting the messages. I called the customer care and asked about it. They said, if I had submitted the docs, then I can ignore that message. Those messages are sent to everyone, and there is no filtering of the numbers. I was moving out of AP, and one day before moving out, I went to airtel office, and asked whether I need to submit the docs again. They said, it is not required. after, I moved out of AP, they blocked my number. I could not call customer care of AP from outside AP, and the customer care people in the state I am staying said, they cannot help it. I had to call my friends in AP and they called customer care number from airtel number (from other phones, it won't work) and with lot of fight they activated it and they told that, if I don't submit the documents, it would be deactivated in three days. Airtel people misplaced my documents, and now, I had to spend lot of time and effort and take help of many other people to activate it again.
I don't think other service providers are any better. Eventhough, the service of Airtel is very bad, still it is better among the worst service providers. So, I don't think I will shift to other service providers soon. I may keep other providers just as a backup.