you ask someone if you can use their battery to charge yours with jump cables
Or... This may sound silly, but you can still use the key, like we all had to do in the old days......
Put the key in the door and turn.
If the battery goes dead flat the door will still unlock manually with the key.
Unlock the door with your key.
By using your key to unlock the door.
By inserting the key in the door lock.
By inserting the key in the door lock and turning.
Use your key to unlock the door.
Stick the key in the door lock and turn.
The battery in the remote may be dead, or the remote or security system may have a fault of some sort.
By inserting the key in the door lock and turning.
pretty sure you can use the valet key that is tucked up inside the key fob to unlock the door.
The Volt has an auxiliary battery back-up that allows the electronic door locks to still operate.