Roblox charges on my Apple ID

I have been dealing with this for the past year or so. Thousands of dollars have been removed from my account using my Apple ID to make purchases on Roblox. Several purchases are done per day and several per week. I am so frustrated at this point. I have reached out to Roblox and no one to speak to. I have spoken to Apple support several times. The last person advised me to use my Apple ID and reset passwords to all accounts. I have located several accounts which have no billing or charges and clearly the one account I cannot locate. I have checked all of my boys accounts and have seen their purchase history which these charges are not being credited to any of their accounts. How can I get some help on this problem? Any help would be greatly appreciated.

Thanks