Bought game was declined still charged

i both got charged in the day for it and didn't get notified when it failed

Did you use Microsoft account funds to make the purchase, and ONLY Microsoft account funds (as in a prepaid gift card)? That would be the ONLY way you'd be charged on the purchase date, I'm afraid. And if you were charged, the order wouldn't have been cancelled,
since you already bought it with your account funds.

What you're describing is very common when people pre-order the game with a credit/debit card. They think the purchase actually went through then, when it didn't. Because game shipment dates are prone to change, you won't be charged until about 10 days prior
to the actual release of the content. If your account doesn't have enough money in it to cover the purchase, it's cancelled.

Have you contacted the payment method (your bank, your card issuer, etc.) to see if they declined a charge from Microsoft about 10 days ago?

When you pre-order a game on the Xbox Store, the only way you are actually charged at that time is if you use only Microsoft account funds. If you have it tied to another payment method, you will not be charged at the time of the order. Instead, you are
charged about 10 days from the game's launch. So if your payment method didn't have enough money on it at that time, the order would fail. You can change payment methods and attempt the purchase again at the
Microsoft Account site in your order history.

i both got charged in the day for it and didn't get notified when it failed

Your bank is the one that lets that happen. If you/Microsoft try to process a charge on declined card, it's up to them if it goes through.

If you expected a subscription to end because the charges would start being declined, you'd be wrong.

Call your bank and have them decline the charges.