Treatment of service tax paid on old rate

 We received services from an architect firm prior to 31 March 2012 for designing our new office. Service Tax was charged at the rate of 10.3% on the invoice issued to us, which is still pending for payment. The architect firm has raised a supplementary invoice to recover additional service tax at 2.06% on the ground that the rate of tax has increased from 10.3% to 12.36%. Please clarify whether we are required to make such additional payment and whether Cenvat credit of the same shall be available to us.