Payment options/payment on account

[Tall Paul]

Hi

I am new to Prestashop and would like to use the system for my shop. However, I have a requirement to allow existing customers pay on invoice rather than pay through the site, while still enabling new customers to pay by credit card through the site. I have searched the forum and found a couple of similar posts, but unfortunately they didn't seem to have replies. Has anyone a solution to this or is there a module I can use. As I say I am very new to Prestashop (and eCommerce systems) and aplologise if my question has been answered before - just point me in the right direction.

Thanks