Service tax on reimbursment expenses

Dear sir,

we are under audit of service tax and the auditor raised query as below

We paid the transportation expenses to CHA for importing goods, CHA give us individual invoices for that  and we reimbursement the same.

Auditor said that Service tax has been paid by us on that transportation charges and we are in assumption that as CHA already paid service tax for the same we are not liable to pay.

pls solve the confusion as early as possible and also provide necessary supporting to give the auditor.

Thanks in Advance