HI,
I would like t know more about your project, can you please share share site url and which payment gateway is creating issue please tell me.
I can quick turn around on this job.
I have been working 7+ year in WordPress/PHP.
About to done various payment gateway liek paypal, sagpay, barkley, pay u, cc avenue , authorize .net,bitcoin etc.
let me know if you have a query.
Rajesh