Service tax detail

We are Pvt. Ltd. company provided a service on which deducted service tax and deposited the same through GAR - 7 challan. Now after 2 month customer not staisfied with service and want refund of amount. So, we have to pay the whole bill amount from which service tax paid to government. Now whether Service tax paid is our loss or else we can take modvat of Service tax paid because of sales return.