Warranty and service issues

I have purchased Samsung galaxy alpha from the authorised Samsung showroom on 27/may/2015 which is still under warranty.after 15 days of purchase, the phone started to hang and battery drained fast and many other software issues for which I visited the service centre and got my system reboot. Now from November, I have been visiting service centres but every time they say that the phone is out of warranty. Neither the dealer is providing me with any solution nor the company as the problems has already been discussed by executive department and customer care people. I also have the original copy of the bill and as well as the print of system's screenshot depicting date of purchase 10/11/2014 and date of manufacture 01/09/2014. please help me in solving the and guide me what should be done and total procedure and steps to be taken for the same issue