You can try calling with numbers in this Support Article:
Contact Apple for support and service - Apple Support
I'm not sure it will help, but it is worth a shot. Apple provides many methods to prevent that from happening. If your son has their own phone/iPad you can turn on the Ask to Buy option or restrict purchases all together.
Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
If it was done on your device you can also use a Screen Time passcode that he doesn't know to prevent purchases. Your son should not have the passcode to your device and if he does it should be changed. Anytime you give someone your passcode you are authorizing them to use your device and that includes making purchases. You can also require a password for purchases.
Set a passcode on iPhone - Apple Support
Require a password for App Store and iTunes purchases - Apple Support