Unfortunately, it’s not possible to start over with the same Game Center account. To start over:
- Uninstall War Robots;
- Log in with a Game Center account (Apple ID) that doesn’t store any WR progress: Settings → Game Center → toggle on;
- Install War Robots;
- Launch the game;
- In order not to lose your your new game profile, connect it to a new Apple ID via Game Center: Game Menu → Game Center ‘Connect’ button.