Asus — Battery drain and not charging

Address: 695013

I have bought an asus zenfone max 5 months before and now im facing certain damages with the battery. The battery is draining out and when im charging it then the battery is not getting charged. So i have taken the phone to the service centre here in trivandrum. And they said that the product iz within warranty period and they repair it within 7 days . After that they called me and said the phone is ready . And I went there and bought my phone back. Then within 2 hours im facing the same issues . The service centre guys are didnt do any work in my phone . Now i went there and reported this. So they took my phone once again and they told they will give it back within 3 days .. what should i do ?