how do i rent/buy movie on apple tv not using the card already attached to the account

You can add additional payment methods, and prioritize the new one, thereby not using the old card.

Change, add, or remove Apple ID payment methods - Apple Support

You can prioritize payment methods by changing the order. The top listed payment method is tried first, then the second, etc.

Account balance is always used first, before other payment methods. You may add balance by doing a money transfer, or by redeeming a gift card.

Check your Apple ID balance - Apple Support

Add money to your Apple ID balance - Apple Support

Redeem your App Store & iTunes Gift Card - Apple Support

Buy Apple Gift Cards - Apple (electronic ‘cards’ for any value, or physical/store-bought card for rounded values)

think you need to make another appleID without that card attached to do that

How to create a new Apple ID - Apple Support