I am using airtel sim. It is worst service I have ever seen. there is always a signal problem. whenever I use 2g internet it always disconnected and connected . and they advertise 4g network if they are unable to provide 2g network how they get 4g network its a common sense. they show that in kashmir they provide 4g signal but in uttar pradesh there is not even 3g avaiable. airtel give very poor service and call rates are very costly.