Still not working

Hi. about a month ago i took my phone in to the Samsung Customer Care in Constantia, west rand with a fault description of: Phone gets really hot, battery doesnt last and phone switches off. When they gave the phone back they just downgraded the phone's OS and said that the OS wasn't compatible. i did tell them that the phone was running with that OS for approximately 3 months with no issues. the next day after collecting the phone the same issues started again. Im due for an upgrade at the beginning of december, im seriously thinking of going to LG. this is my 3rd Samsung. Their service is going backwards