Service tax valuation for tour operator

Dear all,

We are Tour operator service provider. when i was raising invoice thn got confuse about valuation of service tax.

How to charges service tax on tour operator service.

charges to client = Air ticket+hotel booking+other service 

Now problem is that should i charges  service tax on whole value of tour service or only hotel booking and other service coz when i got air tiket booking invoice from my vendor they have already chrges service tax .

so if i charged service charegd on whole value then there will be double taxtaion.

Please help me what should do?

Thanks