I am using airtel for last 4 years. It is very costly when it comes to top-up and internet offers . The only advantage is network availability though it can’t beat bsnl in rural areas. The speed of internet is too slow, even for 3g. But it's 4g service is really fast but very costly.
Coming to its customer service, no one can blame their customer service. It's really good. You get help for the related problems. Very polite and smooth behavior.
