I have used Airtel for a long time 4-5 years in past and had a really bad experience. They activate some or other service themselves and cut the balance. Then reaching out to their customer care which is one of the most difficult thing on earth.
They deactivate the service after a long argument and again after 2-3 days they will start some new service and cut the balance. Anyways, after suffering a lot, thanks to number portability I switched to Vodafone which is 100 times better than Airtel although I will not say it perfect.
Now, I had to move to Bangalore and its my bad luck that Vodafone has some legal issue providing 3G here. And I had to take Airtel again, I though it must have improved by now.
But again the same story, they are cutting my balance saying something SMS TEXT CONTENT and one other value add service. What a cheap company and poor customer service!