Nokia / Microsoft — no sound during call, phone freezes/hangs frequently, applications crashed suddenly

Address:

Surat, Gujarat

I bought NOKIA LUMIA 620 on date.19 oct 2013. I was getting problem within 2 month from this phone.
1 complain to Nokia care U-71, Shreeji Arcade - Adajan Rd, Beside Bhulka Bhavan, Adajan, Surat, Gujarat 99395009. I took this phone almost 8 to 9 time at nokia care. They gave me 5 to 6 time job sheet for repairing. They also send it HEAD OFFICE, Delhi. Every time they insure me that phone is repaired but problem still persists. I demanding for replacement or repayment of phone.But they denies. I record videos regarding this problem as proof. please help me.