This issue is quite common among - though not limited to - MTK (e.g Tecno, Gionee, Infinix, Oppson, Micromax etc) Android phones which have inbuilt batteries. If your phone goes totally dead (no light, sound or sign of life at all) shortly after your battery was low (< 15%) or you switched off at a very low battery, then don't panic. This is caused by a totally drained battery that needs boosting. To resolve this:
1. Remove the battery (If its inbuilt, pry the cover open to reveal the battery)
2. Using an external charger (like a desktop charger), charge the battery for 1-2 hours
3. Slot the battery back in and boot your phone
4. Your phone should come back to life.