I received a invoice today for 29.99 and I do not know what it is for

It is a phishing attempt. Do not respond. Do not divulge any personal or financial information. You can use the address below to forward the suspect email message, as an attachment to Apple.

reportphishing@apple.com

If you provided your Apple ID and password at the bogus site, change your password immediately.

  https://support.apple.com/en-us/HT201355

The links below have information to help identify fraudulent emails.

Identifying legitimate emails from the iTunes Store

Just to note what makes it (of numerous possible things) a phishing attempt.

Real Apple purchase receipts never, never, ever include links cancel a purchase, or manage your account/password. Those are instant giveaways it's fake.

Confirm that your method of payment established for iTunes has not been charged, then delete the email.