Airtel India's worst 4g network

It's going to be 3 months that I am using airtel 4g network. There is sometime the speed satisfying although it doesn't provide a speed that a real 4g network should! Though it gives a speed that I am satisfied with..
But frequently within weeks, it's speed become less than a worse 2g network!!
And whenever I contact customer service for complaint, they are like: we don't have a 4g network in your area!!

And when I ask, " then y are u selling 4g sim cards here and provide 4g network? And how is that 4g network in my phone??"
They are like, we have only this details with us!

And I am to say, "y don't have that terms and conditions that we can be a worse 2g network Disguised as India's fastest 4g network!!"