Motorola SLVR L9
Unable to hear properly while calling

After waiting for long time and lot of choices,

I bought this new Motorola SLVR L9 handset 2 weeks ago, i am using this BSNL Network Sim card, and i am not able to hear properly neither is the caller able to hear me properly

The phone's Basic calling is not working properly

people who called me complain that they can't hear proerly.

This is same case when i call someone.

i have taken it to service center and they kept under observation but nothing changed,

i think i have bought a sub standard item or commodity

now i want to return the phone back to them

but they are not ready to take it