Nokia
Non working of handset N 97

I had purchased a handset during Aug'09 of Nokia N97 (with bill) the most advertised mobile, however the mobile knoks off during the call. When on net the cell goes on hang mode and then it switches off automatically. I had given the same to service centre and they did upgrade the setting. But then too it is not working,

I understand that similar problem exisits for other users of same hand set.