Kesari Tours — the tax calculation

Address:

411004

We have been charged 5% gst on each booking amount of 25k. On a group bookings they have charged us separate gst. On each 25k amount. Also on each amout the calculation of FRX and INR gst is on which basis? Very less information is provided by kesari customer care support. Charging gst on booking amount as well as total tour amount so we have been chared for total of 20% gst for each member. Explaination is required for the same