Wont let me spend my money

Hi. My son added £69 of his christmas money to his meta horizon account, he spent £9 and now anytime he tries to spend money it says theyve noticed something unusual and the request couldnt be completed, please file an appeal to get your case reviewed.  We have spent ages trying to find the place where we can submit an appeal but we cant find it anywhere in his account.  There is no 'Account Status' page, i cant even find a way of actually contacting someone.  Has anyone had this before? Thanks