For this, we would suggest you walk into the nearest service centres as they will be better people to assist you. You can click on the following link to see the details of the nearest service centres and selecting your city accordingly - Service centre.
It would not be possible to install an additional battery in order to extend the range of the Tata Tigor EV. The Tigor EV now uses a 21.5kWh powertrain that drives a 72V 3-phase AC induction motor. According to ARAI, the Tigor EV has a range of 213km compared to the 142km before. The increased range of the Tigor EV is due to the 21.5kWh battery pack, compared to the 16.2kWh battery pack offered before.