My son has bought coins (£287.70) for a game and my account has been charged

You can ask for a refund but since it has been such a long time I believe it is unlikely you will get one, plus these are consumable items and tend not to be refunded.

Here's how to request an app or media refund from Apple (From: Request a refund for apps or content that you bought from Apple - Apple Support - see the article for more detail.) If you bought this in the EU from a third party, see: About purchases not billed through the App Store or the App Store’s In-App Purchase system - Apple Support instead.

1. Sign in to https://reportaproblem.apple.com

2. Tap or click "I'd like to," then choose "Request a refund."

3. Choose the reason why you want a refund, then choose Next.

4. Choose the app, subscription, or other item, then choose Submit.

If you were charged for a subscription that you no longer want, you can also cancel the subscription using the directions in this article --> If you want to cancel a subscription from Apple - Apple Support

Read this support article for information about how long it takes to receive a refund (if you are granted one), and how to check the status of a refund for apps or content that you bought from Apple --> Check the status of a refund for apps or content that you bought from Apple - Apple Support

Here are two sections from Apple Media Services Terms and Conditions - Legal - Apple Media Services - Apple

- "All Transactions are final."

I understand this as meaning Apple is starting from a point where any refund is considered an exception. Apple may provide a refund but can also simply say no without having to provide a reason. I understand this can be frustrating but by using the service you agree to the terms.

- "From time to time, Apple may suspend or cancel payment or refuse a refund request if we find evidence of fraud, abuse, or unlawful or other manipulative behavior that entitles Apple to a corresponding counterclaim." Remember that Apple has no way of removing a purchase from your device. They have to trust you are being honest when asking for a refund. It may be certain refund requests might be considered suspicious.

You can see if the terms are different for where you live by clicking on this link Legal - Apple Media Services - Apple select your location and then your language.

If you feel you want to discuss a refund request, try to contact an Apple representative using a telephone or chat request.

Click here --> Choose your country or region - Official Apple Support Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.

or:

"See a list of Apple phone numbers around the world." Click here --> Contact Apple for support and service - Apple Support

Note that if you allow another person access to purchasing on a device, or through Family Sharing if you are the Organizer, you are taking responsibility for things they do. Apple offers these proactive features:

On your device you can use Screen Time to prevent unintentional or unauthorized purchases from the App Store, in-app, and other Apple services. —> Use Screen Time to turn off in-app purchases on your iPhone or iPad - Apple Support

Also on your device, require a password for App Store and iTunes purchases —> Require a password for purchases in the App Store and other Apple services - Apple Support

Use Screen Time as part of parental controls on your child's iPhone, iPad, and iPod touch —> Use parental controls on your child's iPhone and iPad - Apple Support

If a child made this purchase on their device, consider activating Ask To Buy—> Approve what kids buy with Ask to Buy - Apple Support