Swipe Elite — poor quality of swipe elite 4g phone

I bought a swipe elite 4g phone from flipkart and i received it on 01 september 2017. It was a gift to my mother and i sent it her on the next day. She started using the phone after a week and it was noticed that the sound quality is very poor and the phone cannot be used. I wrote to flipkart customer care and they have given me the details of swipe service centres. I contacted the centre at trivandrum and gave the phone for repairing. After three weeks of continuous phone calls and visits, i got the phone back on first week of november. They claimed that they have changed the mike of the phone and now it works perfect. They even charged me rs. 450 and their attitude is very unprofessional. Again, once we started using, we noticed that the problem persists and it is much more noisy than before. I dont know what should i do next..