If you do not own a 4G LTE phone then do not worry, you are still able to use Jio's 4G service on your 3G or even 2G smartphone (needs Wi-Fi) using JioFi device by Jio that comes that a price of Rs. 1999.
Please check this to learn how to use Jio SIM in 3G phones using third-party Wi-fi hotspots and Dongles.
JioFi device is a LYF powered 4G Internet hub device, you can slide in the Jio SIM into it and connect upto 10 devices using Wi-Fi, you can also connect it to a PC/Laptop using USB port.
The JioFi device would give you the same speed as it will on any 4G device, even if your phone is only 3G or 2G you can get high-speed internet on your smartphone by connecting to JioFi device using Wi-Fi through your phone.