I am receiving messages on my iPhone from this site

You are following the MacBook Air forum, so go to this link and tap the "Following" button. That will remove the subscription and you will no longer receive emails when someone makes a post in that forum.

MacBook Air - Apple Community

Unknown Charge?

1. App Purchase
   1. Curious about a Charge? --> If you see an 'itunes.com/bill' or an unfamiliar charge on your statement
   2. If you have an issue with an app on App Store or billing --> Request a refund for an App Store or iTunes Store
2. Apple Card
   1. You may know your --> See your Apple Card spending history
   2. Also, you may want to --> Manage Apple Pay cards and activity on iPhone
   3. Report an unknown transaction or dispute a charge --> If you see an Apple Services charge you don't recognize on ...
3. Subscriptions
   1. You may view a subscription to an app --> See or cancel your subscriptions - Apple Support
   2. You can also request a refund for a recent renewal of an in-app subscription purchase 

Avoid accidental purchases

1. If it is your device then, please --> Use Guided Access with iPhone, iPad, and iPod touch - Apple ... before handing over a device to a child.
2. If it is your child's device then in the future, enable the Ask to Buy feature --> Request and make purchases with Ask to Buy - Apple Support

It could be Phishing

• Beware of --> Phishing & Other Suspicious Emails 
• Know how to --> Identify legitimate emails from the App Store or iTunes Store 
• Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams —> Use these tips to avoid scams and learn what to do if you think your Apple ID has been compromised.

"what is turned on?: why am i receiving messages on my iphone from this site?"

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Secure your Account:

Does anyone else have access to your Apple Account? If you are not aware of this ocurrence, then I recommend you secure your Apple Account, starting with a new Apple Account password.