Try reading the HTML source <POST> and inspect the hidden fields of the post
A form POST ALWAYS (should) has a referring URL. For billing servers an AUTHORIZED URL or it is rejected -- your link is no good^^
The seller's (merchant page) is always a known factor.
An affiliate has an ID in the URL that should be carried into the data posted -- This passed from the merchant to the processor -- somehow.
So far this is just drama.