How to change the “payment_method”

Currently I am running the free version and am going to purchase but have hit a roadblock with the gateway that I want to bounce off those that are smarter than I before taking the leap.

my financial system is able to talk to the store via json and it pulls a slug based export from the store. when i pull orders through cod it works fine and shows its pending invoice. when i use the export its pulling in as a cash it looks like.

Is there a way change the “payment_method” from “alg_custom_gateway_1” to something else?