Poor Service

We as a Company went to We Buy Cars in Midstream. We saw a car we like. And we want to buy the car. I've then phoned them asking them for an Invoice on the car. So I can arrange for payment to be done. Accordingly to the admin side they don't do invoices. It's not like I'm walking into a shop and want to buy a sweet. This is a lot of money and need to go through the company books. I can't pay something to nothing, I need an invoice to pay what to what. I've then contacted them again and requested to speak to an manager. They've put me through to a guy name called Francois Venter. And he explained to me the same thing and thats the way their business operates. They'll send me an tax invoice once i've made payment to them. But they can even help me to get finance through a bank. How do the banks pay them then? Is this also without an invoice? I'm a serious buyer. And this is blocking me now. I've send a mail this morning again asking what can I do? Is there maybe a Over to purches letter I need to sign. And Now I'm not even getting any feed back. It seems like the way they want to work is. Either you need to buy the car cash or through bank finance. I need some sort of documentation saying I'm paying this for that.