Huawei — Honor 7

Hello this is Dr Natrajan.. i have bought a honor 7 phone 1 month ago in Malaysia and gifted to my sister in India.. she is now complaining that there is microphone problem where the person who calls her cant hear her voice clearly... this phone is still in warranty hence can she do go to the outlet in there as she is curenly reciding in trivandrum kerala..its an international waranty right? or if cant is there any other way we can reboot the settings ourselves if you could teach us.. please do help me as now she is complaining i have given her a faulty phone.. thanks a lot..