Updating new payment method

can someone please help me? My phone is telling me to update my payment method because my last card was expired. I followed the instructions and changed the expiry date and Cvc number but it would not update. I tried removing the card but there was a subscription attached to the card so it wouldn’t let me remove it. I got rid of the subscription and still couldn’t remove it. I tried adding a new payment method and it says the new card is already a payment method. Furthmore I had previously tried making purchases through a game and it declined it and told me to update my payment method, however on my banking app my current card has already been charged and the purchases are not on the app. I have no idea what else I can do, I can’t make any purchases in the App or iTunes Store and I can’t update my card.