Billing

Hello. I had a subscription be renewed last week and I bought a few things from in app purchases, and I still haven’t been billed. My total is up to $22 and I want to be billed now so I have some money left over on my bank account before more bills take more money out, which would leave me without enough money to pay the one bill apple wont bill me for. Can someone explain why I’ve waited a week but still no bill from apple?