The website is running on an "order by email" basis, whereby the customer places an order and waits for the admin to contact them for the money transfer.
So basically, the customer places an order (which is set to pending...)... and if the client decides a day later that he wants to cancel, he can login and go into their orders and click "cancel order".
This will then cancel the order and email the customer and admin that the order has been cancelled.
There was an addon I installed, but it was very "buggy" as it was from 2006 +- ... so that was uninstalled... and the search continues. :(