"If I were you, no matter who you choose to integrate, I'd encapsulate it behind your own payment "service" so that even if you have to switch or you need to add more then one (highly recommended), then you can."

This is the best advice in the comments. I've seen my own code and others become overly coupled to a specific provider's terminology, mechanisms, and expectations - leading it to be exceptionally painful when you inevitably have to migrate away to a new provider (or support more than one).