End point receipting of touchnet credit card transaction requiring IPs for guest user site for firewall rule

Question

I'm in a real pickle! I have a missing critical, overdue deadline to use a TouchNet Upay site to receive deposits via credit card. Desperate help is needed.

My code currently posts out to touchnet successfully and touchnet successfully receives a payment. At that point touchnet uses a post-back url that I have defined to receipt back the success of the payment with a transaction Id.

I create a rest resource to receive this post information which is proven accessible through postman (permissions have been set correctly).

TouchNet on the other hand can not see it, and logging backs this up, because they require a firewall rule in their firewall to allow the posting. They continually request a static IP to open up in their firewall.

The Salesforce community site I am running my rest endpoint is running through a CDN and only has an IP range. The IP ranges of Salesforce orgs is planely available, but they don't align what I am seeing coming from the domain my rest API lives under.

I have had a case in with Salesforce for a week and a ticket in with TouchNet for the last month. Both have made me reiterate my needs over an over. Let's see what this community can do!

Does anyone have any insight into what I might tell them for IP ranges?

Note: I did ask them to write a fully qualified domain rule in their firewall and so far they have refused to do that technique.

For those interested. Here is my very basic end point awaiting a data package of receipt information for which I will process and put into appropriate objects (not included yet)

@RestResource(urlMapping='/applicaitonpaymentreceive/*')
global with sharing class ApplicationPaymentRest {

    @HttpPost
    global static String receiptDeposit() {
        RestRequest req = RestContext.request;
        Map<String, String> params = req.params;

        if (String.isNotBlank(params.get('session_identifier'))) {
            String paymentStatus = params.get('pmt_status');
            System.debug('TouchNet Postback request headers: ' + JSON.serializePretty(req.headers));
            System.debug('TouchNet Postback parameters: ' + JSON.serializePretty(req.params));
            System.debug(params);
            system.debug(params.get('name_on_acct'));
        }

        return 'HTTP_OK';
    }

    @HttpGet
    global static String messageForGet() {
        return 'THIS ENDPOINT IS FOR POSTS ONLY';
    }

}