If you are looking to disable any available payment types (DB, RF, PA, etc) for a specific merchant, so as to disallow the use of it via the BIP or via API call, it is possible via the following steps:
Step 1:
Navigate to the BIP -> Select the merchant in question
[this is important as you do not want to disable the given payment type for more merchants than the one that requires this setting!]
Step 2:
BIP -> Administration -> Processing -> Processing Restrictions -> Prevent Payment Types -> {select the given payment type to be disabled}
