Is your phone not turning on? Is it bricked? Probably, but first try this:
- Press the power button for about 10 seconds and let it go.
- Plug it into the charger and leave it there for about an hour. Make sure to use the original charger and cable. It may also be a good idea to have a look into the charging port to see if it's not clogged with dust or anything of sorts.
Still dead? It's a hard brick. Only a service center will help you now. However, be ready to be offered a different device as a permanent replacement :)