OP, as an FYI, it isn't your magic bands that are being charged. The charges you're making are going to your resort room. The magic band (or if you don't have a magic band, your "keys to the world" card) is just a way to have those charges placed on your room.
And as others have said, each level of resort has a dollar limit attached (value = $500, moderate = $1,000 and deluxe = $1,500). Once you've reached that dollar limit in charges, they will automatically charge to the credit card you have on your reservation. That's why, if you plan to pay with gift cards or some other method of payment than the credit card used on your reservation, it's important to "pay as you go" so that the credit card isn't charged.
And, as an FYI, if you have more than one credit card on your room reservation (say, two unrelated friends staying together, each using their own credit card), it doesn't always work correctly to have the charges split onto two separate credit cards, even if you set it up that way. I stayed with a friend last year, and we were assured that our charges would stay separate, each on our own credit card. Luckily, I checked at the end of the second day. All of our charges were going to my friend's credit card - both mine and hers. And since we were at a value resort, we could easily have hit that $500 charging limit, and all of my charges would have gone onto her card. What a mess!