Tds not reflecting in form26as

I am a salaried individual and returns are filed regularly. 

From AY 2007-2008 onwards, TDS deducted from my salary are not reflected in Form 26AS. 

Beacuse of this IT Dept have sent demand notice for payment of TDS amount plus interest.

I submitted original Form16 but they say that they cannot update TDS amount based on this. 

My CA advised me to request the companies to file revised TDS return. But one company has been sold way back in 2009. 

Question is:

1. What documents are to be submitted to IT so that they can give me credit for TDS?

2. Can revised TDS return be filed by the comapanies now?

3. For the company that is closed/sold, how can they file revised TDS return for me now? Whats the way out?

Please advice.