First Flight Couriers — more than 50% gst charge

I sent a parcel to india from canada to my parents with kbee support. The value was around 30 cad which is around 1500inr. They guy charged 844inr from my parents as gst as it was written on the parcel and did not give any receipt too. How much u r supposed to charge and why no receipt. I have been trying to call vishakha bhawan delhi branch since few days as the add was from them and sent an email to them. No one is picking the phone anf no reply of my email. Kindly explain.

Smita