Airtel — too slow 4g speed

I switched over to airtel, a month back when it came up with the famous 399 pack for prepaid phones, what made me to port was the true 4g speed that i experienced on my father's phone.in the beginning the speed was satisfactory, but now it has come to speeds slower than 3g, earlier i used to go for bsnl 3g on my other sim, they're slow but atleast they provide speeds upto 1 mbps (Sometimes even faster) in the morning hours but airtel is even more pathetic, it feels as if they have installed speed barriers. The average speed is somewhere around 100 kbps, also now the validity of 399 pack has been reduced, given the speed that was provided earlier i was ready to go for it but now i wonder. However airtel went for a remarkable market strategy to compete with jio, but you know what, cheap strategies don't last long.