[Resolved]  Samsung Duos C5212 — dual sim not functioning

I purchased a Samsung DUOS C5212 model set on 13.06.2009 at The mobile store limited, 7/I P.R Complex, Bharathi Road, Cuddalore. But from the day of purchase, the SIM which I had already (postpaid Airtel), if inserted could see the contacts. I activated another SIM (Prepaid Airtel) and inserted into the Cell.Now I could not view any contacts, from both the SIM as well as the contacts in the phone. So I purchased another new SIM and this also when inserted shows the error "entry emplty". But if the same sim was inserted into my old mobile I could see the contacts. Also the person at the receiving end could not hear my voice clearly, certain times there is echo at the other end and the other times the voice is not clear. The new cell was purchased only 10 days back. Please make arrangements for me to exchange the set or I will take the matter to consumer court. But in the show room they refused to exchange the set. I tried 3 new SIMS with the set but all the three when inserted refused to show the contact details, but when only my old postpaid SIM was inserted, I could see the contacts of that SIm as well as that in the phone. Expecting your favourable reply for which I would be much happy for I have spent 7000 in that set and 10 days up and down the show room wasting my time, petrol and energy.

My contact no. [protected], pls reply immediately