How to process GET/POST response from Symbolic URL

Good day,

I am stuck and hope someone can help me out.  We are running on 8.2.1. and have a third party vendor (First Data), that we have embedded the call to their site within an applet using a symbolic URL.   The vendor is to start returning values back to us using a dedicated HTTP GET/POST.  Currently we are trying to figure a way to capture the updated information the vendor is returning and update a record within Siebel.  We have started using an .asp page, however we are unable to update any records at this time using that approach.