HTC mobile P3470
Phone is dead not getting activated

I purchased HTC P3470, from hypercity store Malad MUMBAI.IMEI no is 357394017714607 with S/N DP814GL00004 and P/N 99HERO16-00 A.

invery first month mobile developed fault and its motherboard was changed by service center sec 32 chandigarh in warranty period. Now it is hanging and scren is not responding to stylus.when shown to service center chandigarh it has been advised to replace screenfor cost rs 4500/-.i feel very sorry with product of high cost behaving like this .what company can do now, pl help