Airtel — 4g data speed less than 100kb/s

I have airtel postpaid connection, and having infinity pack of 799 in which i got 40gb 4g data.
But from last 1month i am getting 4g speed only at youtube. No other sites i opened getting faster speed than 100kb/s. But in youtube i am getting speed of 5mb/s.
Airtel is just fooling me by giving data.
I have also complaint to 121 many times, but they are not doing anything.