Nokia Phone Model (7710 GSM) — repaired many times under warranty but in vain

Hi,
I'm Aakash Sheth, bought nokia 7710 in Rs.18600 facing problem from beginning used it for about 3 to 4 months withou any problem but using it for 2 to 3 yrs with problems mentioned below
Nokia Phone 7710 repaired many times under warranty for phone hangs a lot (without memory card insterted in it) and network problem (always), previously repaired in rajkot NOKIA CARE CENTRE (out of warranty) paid Rs.3800 but remained the same .Is there any one in nokia who can help me closure to repair my phone in FOC basis as i'm screwed up with the phone. I'm totally helpless now.

I'm already tried to sumbit in kolkata's nokia care centre i.e in girish park but one of the executive told me that sir " yeh model to bandh ho gaya hai aur humare pas 7710 ka koi parts avaiable nahi hai aap koi aur care centre me try karo " so i request you to suggest me a proper channel to get my phone repaired