I can help you to integrate online payment gateway for your website/web app to enable your clients pay for using the services you provide. There are many payment gateways available, to choose which gateway to use depends on your application, transaction volume, your country among other things, I'll help you out from scratch until you recieve your payment into your bank account. I've dealt with these gateways before, Stripe, Paymob (AKA WeAccept), Payfort (Amazon company), PaymentWall, ... Also, I've a previous experience with integrating online payment methods into Arab countries such as Egypt.