payment module wordpress

Create Payment module for our Wordpress Directory Site. [login to view URL] Our installed theme is: [login to view URL] Now we have paymenmetode, Paypal, Stripe. (We dont want it) We need a module for Billogram (invoice payment) : [login to view URL] 1. Create module for Billogram The price on the products package in directory is without tax. When it creates invoice in Billogram you should add 25% tax. 2. On registration process. (front page) Emailadress Username Companyname First Name / Last name Adress Zipcode State All code without modules shoule be created in child.