I made a Pokémon GO account on 1 of my google accounts and I bought a gift card for that account. Now the game is asking payment methods for my other google account. How do I switch the account for payments?
The account you're using for the Google Play Store is not the same as the account that you're using for Pokemon GO.
In order to use your Pokemon GO account for purchases, you need to log out of your current Google account on the Play Store and log in using your Pokemon GO account.
The account that you used to download Pokemon go will be the account that will be billed. So if you updated Pokemon go using a different account now have a different billing account. So delete Pokemon go and reinstalled with the account that you would like to pay.