You cant change it, jio automatically connects to higher band according to your signal strength, means the more you are near to a tower, it connets band 2300 to give better speed since you have better coverage, because band 2300 gives more speed and less signal strength, band 1800 gives half the speed of band 2300 but two times better coverage than band 2300, just like that when band decreases-coverage increases , though speed decrease
Less band= less speed and more coverage
Download netvelocity app and click on + and select rf information to see which band you are connected to.