This issue either means that you've been negligent in the protection of your own account, or if you have already checked your purchase history at https://reportaproblem.apple.com , and do not see the charges in question, the more likely scenario is that your payment card information has been compromised externally from Apple, and the thief happened to use your information to make digital purchases on the iTunes or App Stores.
You should first do your due diligence and check the "Report a Problem" site linked above, and if you still have questions, you should first contact Apple via phone at https://getsupport.apple.com > iTunes & Apple Music > iTunes Store... and proceed accordingly to get in touch with a phone representative.
People blaming Apple for their compromised cards or negligence in securing their accounts are ignorant.
Compromised credit and debit cards happen all the time in all locations at an increasing rate every day.