How to save Pokémon you've caught in Pokémon Go when your phone freezes - iOS

1. As soon as Pokémon GO freezes, go to your phone's Settings menu or the fast menu (your Control Center, on iOS) and turn on Airplane Mode.
2. Go back to Pokémon GO and close the game.
3. Wait until the game says that it has lost its internet connection.
4. Restart Pokémon GO.
5. Turn off Airplane Mode.
6. Check your bag for your newly captured Pokémon.