How does GST works out on Inbound tour packages

We are confused by the fact that Tour Operator does not have ITC. You see, many of the travel agents buys holiday packages / tours from another firm who charges GST. If we again put 5% GST on purchase cost then it is cascading the tax when no ITC is available. 

e.g. Agency 'A' supplies Tour Services to agency 'B' for Rs.50K+5% GST = 52500 total.

Now agency 'B' sells this to customer as Rs52500+ 5250 (Commission/Margin) = Rs.57750, Additionally as agency B is GST Registered, then he will add GST of 5%. So customer will pay Rs. 57750 + 2887.50 (5% GST) = Rs. 60637.50.

So cascading effect if no ITC and moreover customer will go to direct suppliers than agents. Ideally, agency B should pay GST for his commission earned i.e. Rs.262.50 (5% on 5250).

Is my understanding correct? 

Please help asap as we are stuck with all bookings. 

Thanks