You can disable payment methods from your Customer Area (only in Test)*. Make sure you are at the merchant level, as payment methods are not shown at company level.
Then go to Account > Payment methods. Select the payment methods you want to deactivate or delete on the left side of the page by checking the boxes, and click on the desired action at the bottom of the page.*
* To disable payment methods in Live please submit a request via the button below.
** In case you cannot find this option, please reach out to your admin user.