Lenovo k3 note only works when plugged in - HELP!!

A

AC Question

I'm facing an issue where my Lenovo K3 Note only works when it's plugged in. I can tell the cable is working because it's able to operate the phone but not charge the battery. I know that this is a hardware issue but is it a faulty battery or a faulty charger. The charger and cable I'm using are the ones that came with the box. ANd they seem to be working fine. However when I unplug the cable, the phone shuts off and only starts up again when plugged in. It looks more likely to be the battery. What do you guys think? Or is it the phone itself with some issue - possibly the connector etc. Please help me asap, because my phone which is used for calls, only works when plugged in and a mobile phone is meant to be portable.