iphone 5s got issues even after repair

Hello, I am from India. I bought the iPhone 5s on 19th feb 2014. I start facing some speakers issue in phone on 26th feb. I went to the service centre and they told me that It need speaker replacement. So I talk with the local advisors on phone and they say the same thing that they cannot replace the whole unit. So I deposit my phone for repair and I got my iPhone back on 13th March. Speakers are working very well. But later I noticed it got some other issues. There is no option of Touch id. Only option there was is Passcode. I have the latest software 7.1 on my iPhone. Now it is getting overheated and sometimes lagging and rebooting itself. I talked with service centre people and they said they will restore my phone and all other troubleshootings and see if the option of Touch id occurs. I had an conversation again with local advisors on phone and they assure me that they will replace the whole unit if the issue doesnt solve after troubleshootings. But on the other hand, the service center guy said they can only repair my iphone again not ready to replace it. I am really upset and mad at the Apple Service now. The phone is not even one month old and I am going through alot. I spend 51k on this phone and all I am getting is stress. I am going to visit the service centre on 18th March. I got Touch id and overheating issue only after the repair so basically the service center is responsible for these issues because these options were working very well before repair. Plz someone suggest me or advice me what should I do now? I m very upset with the service of Apple. Really didnt expect such service from Apple especially in manufacturing defects like my phone. Just making me upset. I also want to know How should I get it repalcement because I am not ready for its repair again now on any condition. It is wastage of time. Because there service is poor they dont even handle customers properly, very poor service by them. Good at making customer Fool.