Can 4G be used on a 3G phone if 4G bands are supported?
Is your phone called the Micromax a350 Canvas Knight? If so, I'm sorry, but your phone DOESN'T support 4G, according to the specs sheet found on gsmarena.

Don't be excited to see the LTE in the *#*#4636#*#* options, because that menu lists all the possible bands there is, although your phone might not support all or some of them.

The maximum you can connect to is 3G, you therefore can't use the 4G in your area. The limitation is not software-related. It is hardware-related. The hardware component responsible for supporting 4G band isn't in your phone.