Possible solutions:
1. Check from car that charging has been stopped.
2. Three clicks on the keyfob rapidly should terminate the charging and release the lock.
3. All else failing and assuming you've contacted the customer service of the charging station (if you are on a public charger), there is an emergency release in the trunk. Depending on MY, there might be a small part of the fabric in the trunk on the charge-port side which you can open either by pushing or with a knife. Behind that, there is an emergency release cable. Do be careful, as next to that is another emergency cable to disconnect the car from the big battery. You do not want to pull that. Pulling the emergency release should release the lock, but you should be 100 % sure there's current i.e. it is not charging. If you happen to have 80kW going to the battery and you pull the cable..
Here's a video showing the emergency release: