That can only happen if someone knows your Password/Passcode to be able to authorize the charge. Never give this information to anyone else as that is giving them authorization to make purchases. Change the Password on your account and Passcode on your device immediately.
Review your Purchase History here:
View your purchase history for the App Store and other Apple media services - Apple Support
You can try to request a refund, but it is not guaranteed. Apple may provide a compassionate refund in some cases, but it should never be expected.
Request a refund for apps or content that you bought from Apple - Apple Support
If you are unable to determine how the charge occurred, then follow additional steps to take for when your account has been compromised with help in changing your passwords.
If you think your Apple ID has been compromised - Apple Support