Get AR or CR Unpaid Charges
using System.Net;
string uri = "https://fusion.superion.com/FusionOSServices/v1/ONESolution/AccountsReceivable/UnpaidCharges";
string xmlText =
@"<GetUnpaidCharges>
<AccountID>PMI01</AccountID>
<InvoiceID>OptionalInvoiceFilter</InvoiceID>
</GetUnpaidCharges>";
using (WebClient req = new WebClient())
{
string stringResult = wc.UploadString(new Uri(uri), "POST", xmlText);
XmlDocument response = xmlDoc.LoadXml(stringResult);
// TODO
}