Lenovo K4 Note 4G/LTE issue

[ukchy123]

I have a Lenovo K4 note and under setting LTE mode only is enabled and in Delhi Airtel 4G Band 3 and 40 are active and In Note K3 is was catching 4G network but in Note K4, only 3G Airtel connects, , when I go to manual network selection it shows Airtel 4G but it is not able to register there, signal is good in my area, what could be the issue.