Paying for things on apps
When i buy things such as: Snapchat premium, TikTok promote etc. It charges my dad’s card instead of mine and when i go into change the card it doesn’t let me, as in there isn’t even an option.
iPhone SE, iOS 17
Sounds like you are using Purchase Sharing on a family plan. The Organizer can turn Purchase Sharing off, then each member will be able to use their own payment method or you can add funds to your Apple Account from a Gift Card and any purchase will first come from your Apple Account with only your Dad's card being charged if there is not enough money there to complete the purchase.
How to share apps and purchases with your family - Apple Support