Payment gateway integration for custom WordPress plugin (already built)

I've had a custom plugin made for my WordPress site to enable me to offer a pick 'n' mix customisable dog treat subscription. The plugin is currently integrated with GoCardless but unfortunately, I've just realised that processing a transaction takes 5-7 working days due to the fact that a direct debit mandate has to be set up (they can't process card payments). The problem with this is that I need to send out products immediately. What I'm looking for is somebody who can connect a suitable payment gateway that will enable me to see if a payment has been successful so that I can send out the products immediately. What makes the plugin unique is that it enables users to login into their members' area and edit the contents of their subscription at any point WITHOUT changing the subscription payment date. The payment amount then needs to be updated along with the contents of the subscription. (The plugin is setup to do this at the moment but with Go Cardless) I've been told that it might be an option to use Stripe. PayPal isn't an option because I don't meet their trading history requirements. In summary, I'm looking for someone to modify my custom plugin by removing the GoCardless payment gateway and replacing it with a more suitable payment gateway which allows me to instantly know whether a payment has been successful or not. It must be able to use the existing functionality of my plugin i.e. when someone edits the contents of their subscription the payment date stays the same but the amount changes in accordance to the changes made to the contents of the subscription. I hope this makes sense. Please contact me if you have any questions.