Custom payment module

I need a custom payment module: The system at Epay offers a system that allows the customer to pay per. month This system must be integrated into their system, so the customer can choose to pay with Paypal or ePay payment. The system must be a way to remember which user has bought what, and be able to cancel his subscription. The user should also be able to edit his account, because if he pays monthly, and now wants to pay every year instead, then he should be able to change that, for both parts. Paypal and Epay. If the customer opt subscription, the customer's subscription only lapse from the end date for when he bought Be professionel, since I need it in 5 days