how to convert my 3G phone to 4G?

[AC Question]

My Device name is Micromax canvas gold A300

 

[hallux]

You need only post one time (you posted THREE). One of the other posts contains a link to another thread where the question is answered. Bottom line, this is generally a hardware limitation of the device, it simply doesn't contain the hardware needed to connect to the faster network and that hardware can't be added.