When using multiple payment gateways it may be helpful to abstract a bit by creating a payments class within your codebase. This class or library could pull in multiple payment gateway libraries for the language you are working in and include functions to process a payment that allow for "gateway" to be one of the variables sent to it.

This function could then use the gateway variable to determine which logic to employ to complete the payment.

If this is not a custom codebase and is a product you are purchasing from a 3rd party your best option is to contact the vendor for their recommendations.