First of all I want to say don't go for all that advertisements of airtel 4g all are fake.
I got new phone few months back and as I live in Chennai only few ips's have 4g network option so I decided to go with airtel 4g because of all that false advertisements and seriously guys since that day I've not seen LTE sign on my phone's notification bar.
I'm there is not a single place in Chennai where I could able to get any 4g network all I see is no network available.
I'm planning to switch to reliance jio 4g heard they have some good speeds let me know if any of you've used it in Chennai.