ESDM Web Service Documentation

We want to create a portal where customers with outstanding invoices can pay by credit card to bring their accounts up to date.

I could use an Authorize.Net account to accomplish, but it would be much more convenient to use ESDM, thus everything is handled via one electronic CC processor.

I’ve seen past requests for documentation with regards to the ESDM web services, but there are no answers.

Has anyone been able to get their hands on this phantom documentation?

Has anyone been able to call the web services directly to process payments outside of Epicor?

Thanks in Advance,

Steve