Micromax Fire 3 replacement issue with the company

I purchased Micromax Fire 3 mobile phone on 17-04-2015. After one month one of its speaker stopped working and the other one became noisy.
I gave it at service center, and they said they replaced the speaker but it still wasn't working even in front of them.
A month later I gave it back at the service center on 11-07-2015. Promising that they will repair it in a week, they kept it for two weeks. After second week they said they had to escalate the problem to the company as they cannot solve it. So they sent it to company. I got no notification of it. It has been nearly a month and I am without my phone. Company doesn't respond. As the phone is in warranty I want full replacement of the phone. Why the company is taking so much time in just replacing the phone when it is still in warranty? I sense that they are just passing time as the service center did. Micromax is India's one of the biggest brand and this is never expected from the company.
Further details are as follows:
Job Sheet Bar-Code: W020328-0715-17861755
Model: Micromax A096

ESN no.: 911373950560754
Name: Naveen
Place: Udaipur, Rajasthan, 313001