Hi, I have developed two websites that use multiple payment systems without fault. I am not sure what your service is or how you want to go about setting payment, but i can give you some simple advice on the easiest way to get this working. I would recommend STRIPE. I would design a wordpress based website and simply linked a payment page to STRIPE using a couple of plugins. These will cost you money , but you will need on going support in your using payment systems and a payment of around $50 for a plugin with a years support isn't bad. If you are out and about and need a customer to pay, you can simply go to your website, then to the STRIPE page you made and put in the amount or select a recurring payment and get your customer to input the details. The site i designed sells printer subscriptions as well as one off payments. The customer can go to this page and select which payment type they want to do i.e. one off payment or a recurring monthly or annual payment, and thats it! You can do this through your phone, or get the customer to log onto the webpage themselves and make payment. If you need anymore help or advice let me know and i will guide you as best i can.