I have 2 airtel prepaid connection, I have got 12 month offer of 348 in both sim, but I did recharge on my old prepaid sim, the offer is, in 348 I will get 1gb daily 4G data and unlimited local + STD calls, the calls quality is good as always but the 4G network became worst after recharging of 348, I have insert me new sim and turn of the data it works on 4G with great speed, but I again insert my old sim it working only on 2G speed, mean I am not able to use 4G speed, I have called customer care a lot of time but they always say same thing you setting is not correct, you have to enable 4G mode in your phone, 2 times I have swapped my sim but no benefit, if here any airtel official available than please enable 4G data on old sim I am really so much bored with this 2G speed.