I have been using an airtel 4g sim since last September ( 2017) . It was the first time I bought a 4G sim when I bought a new phone that time.Pros: at first the network speed was satisfactory. There was no problem with calling and receiving. The data speeds are fairly good. Customer service is also satisfactory.Cons: 2 months after I took the sim, the network became tremendously slow. YouTube video of 5 minutes took me 8-10 minutes to watch because the additional time was needed for buffering. The speed became like 2G. It was really very very irritating. Then I took a Vodafone SIM.Overall: please check before buying if Airtel network in your area is good, & then buy.Thank you: ) Please like the review if it helped you.