17 May 2012
For Demand notice you cant file Rectification u/s 154. you must have received computation notice u/s 143(1). i guess you ignored it. now the demand notice is received showing the arrears.the only is find the notice u/s 143(1) then file a rectification u/s 143(1) manually not electronically. the Demand notice also contains a note that please contact your ITO for any clarifications.
19 May 2012
you cant sent any notice to CPC Banglore. They just intimated that these demands are pending against. it also contains a note for further information you please contact your ITO. So you need to Contact yours ITO or write reply letter and file at inward of your respective range.