Read the appropriate section below depending if you have the phrase or not.
a) You still have your Recovery Phrase
Follow the restoring instructions on our article here.
If you have lost your old phone and there's any chance that someone finds it and guesses your PIN, for increased security we recommend that you send your assets to a new Recovery Phrase. Read the instructions on the section "Someone got my Recovery Phrase" here.
b) You no longer have your Recovery Phrase
If you still have your old phone configured with your wallets, you can get the Recovery Phrase from it. Read more here. Then follow the instructions from section (a) above.
If you no longer have the Phrase or access to the phone configured with your wallets, unfortunately it's impossible to restore access to your assets.
Koala Wallet is an anonymous and non custodial wallet. This means there are no "accounts" and it's only possible to restore wallets with the correct Recovery Phrase. Since the Recovery Phrase is never transmitted out of your device, it is your responsibility to properly back it up. Read more about it here.