Fix Joomla problem (recurring payments)

We are seeking a skilled developer that is familiar with Joomla, Virtuemart and Recurring billing (using credit cards). The candidate will need to have solid knowledge of this type of integration so it can be done quickly. Candidate will be provided with the necessary details to complete this project. The payment gateway used is [login to view URL] which is compatible with Virtuemart (and we're currently using [login to view URL] together with “Joomla! 3.6.2 Stable”/Virtuemart2). More information on the payment gateway can be found here: [login to view URL] The task is simple: We have a website including a webshop where a person can buy a product with a recurring monthly price (a sim card). The customer pays using a standard credit card. The webshop has previously been integrated with the payment gateway and everything has worked nicely for a couple of years. Then the site was upgraded from Joomla 2.5 to Joomla 3.6.2 and now it doesn’t work anymore. We know that the payment gateway is not the problem as the company keep their API’s updated (and they can be reached by support). So I need someone to fix this problem so that we again can deduct the customers credit cards each month. The monthly payment deduction from the customer’s credit cards is run using a script on the server (Joomla). There is extensive documentation in English in regards to how the [login to view URL] API works. A small second task is to adjust the minor problems (design bugs) that have appeared after the upgrade. We have both a production site and a test site. This means that testing can be done directly on a dedicated test environment.