CANNOT GET ANY HELP FOR FAULTY PHONE

I went to upgrade my contract during my lunch on Wed 12 Aug. I got the Sony Xperia M4 Aqua. I went back to work and used my old phone for the rest of the day. When I got home late that evening I opened my phone to start setting it up. The charger did not work. I tried multiple plugs but it still did not work. I had to use my old phone charger and it took 4 and a half hours to charge!! WAY too long! I left the phone on my bedside table over night, all apps closed, and the battery declined 7% during the night without me even touching it. When I am at work my phone needs to stay in my locker, so I left it there from 7:30 to 12:30. When I went to fetch it for lunch the battery had declined to 55%! This phone has a guaranteed 2 day battery life! Within 24 hours of getting the phone I took it back to CellC where they told me it would have to go in for assessment. The consultant agreed that the phone was faulty. Today, Tues 18 Aug, I got a call saying the phone came back with a normal report. The consultant told me when she tried to charge it, it WOULD NOT charge and the battery was STILL DECLINING. They want to send it for evaluation again and refuse to give me a new one!! I am so angry!