Indian Oil Corporation [IOC] — unauthorised charges

Address:

Kamakhya colony, maligaon, Kamrup Metropolitan, Assam

The distributor of Shivam gas agency in Guwahati, maligaon named Dhiraj, charges a sum of ₹50-60 delivery charges everytime he delivers a cylinder. This amount varies from C2C.. first of all is it legal to take such kind of delivery charge? If yes, why is the amount not same for all?? Further, if it's legal, there should be a seperate issue of slip or receipt..whybis it not transparent? And it has also happened that he instead of delivering the cylinder to the person who booked, illegally sells the cylinder to someone else in black..we don't even get 1 cylinder in a month even after booking it in the right time... please look into the matter as soon as possible