Service tax liability

Dear All 

We are doing business of Transportation where the service tax payment liabity assinged to consginer or consignee. We are also not chargeing the service tax in our bills and cleary mentioned in our all documents ( Bill, LR , ) that service tax will be paid by customer only. 

We are securing the orders from Pvt Limited and limited compnaies and execute the same through our vendors keeping nominal margin. 

Please suggust in above there is any liabilty of service tax on us. Above process which we are adopting is correct ? Please suggust.

Regards

Anubha