What happened to Sony? Selling faulty products!!

I recently received a Sony Xperia M5. The device switches off by itself even though there is lots of battery, and the only way it can be switched on again is by plugging it into the charger. Upon further research this is a known problem of this device. I contacted Sony South Africa and was told I had to contact the provider I bought the phone from, i.e. Cell C. I knew that Cell C would never help me without taking the phone in for weeks, and considering this is a known problem on the part of Sony I feel that Sony should be sorting the problem. Surely when you mess up the design of a product you should be only too happy to be given a second chance to fix your mistake without inconveniencing your customer further? Why should I be sent from pillar to post regarding this, only to have my phone taken away from me for weeks on end. And according to feedback from other customers, a new handset will be issued with the same defect and the cycle continues. What happened to you Sony?!