Employer has deposited tds with wrong pan no

My past employer had deducted TDS of about Rs 35000 from my salary for the year 2011 -2012 ( tax year 2012-2013). However, they have deposited this TDS against a diffent PAN no. Even the PAN no in my payslips is wrong which I did not notice before and the form 16 given by them does not mention my PAN no. I just received a demand notice from the IT department for the TDS amount. What do I do? Please advise.