Constant issues with Note 4

<p>I bought a Note 4 cash on 4 July 2015. You are well aware that these devices aren't exactly cheap. Anyway, a year later (September 2016) the phone starts acting up and gets sent it for repairs via Samsung to SmartLab. The phone gets returned a week later and the job cars indicates that the main board was replaced. Additionally, since then, the spen won't register anymore. Lovely. </p> <p>Anyway, here we are again today... Device acting up, robooting itself and switches off when the battery reaches 50%. </p> <p> </p> <p>Please assist to get this sorted. This device is in pristine condition but I cannot have it shut down on me like this every so often. </p>