There is a purchase on my account and I don't know who made it. What should I do?

First things first: if you see an unknow purchase on your account, assume your account has been compromised. As soon as you have the opportunity, change your password and review your security settings. Once you have done this, the relevant app store provider can help you if you have unauthorised purchases on your account. 

Depending on your device, please follow the appropriate steps below:

Apple App Store purchases

• Change your Apple ID password: https://support.apple.com/en-gb/HT201355
• Requesting refunds for App Store purchases: https://support.apple.com/HT204084
• Read Apple's security guidance and advice: https://support.apple.com/en-gb/HT201303 

Google Play Store purchases

• Change your Google account password: https://support.google.com/accounts/answer/41078
• Reporting unauthorised payments on Google Play: https://payments.google.com/payments/u/0/unauthorizedtransactions
• Sign into your Google account and check your account's security settings: https://myaccount.google.com/security 

Amazon App Store purchases

• Change your Amazon account password by logging into your account on your regional Amazon website, then visit the "Your Account" page. From here select "Login & security" to change your password, as well as view and change other security settings.
• Requesting refunds for Amazon App Store purchases: visit your regional Amazon website, and contact a support agent for more help.

Samsung Galaxy store purchases

• Change your Samsung account password by logging into your Samsung account on the Samsung website, then clicking the profile icon at the top right. Click your name, then select the Security tab. When prompted, enter your password, then select "Change Password" in the Password and security section.
• Requesting a refund for Samsung Galaxy Store purchases: contact the Samsung support team for more help. In the Galaxy Store tap Settings, then Help, then Contact Us to send them a message.
• Samsung Galaxy devices also have access to the Google Play Store so we recommend you also follow the steps under Google Play Store purchases above