Please refer to the following link, and then click on the proper location (Live or sandbox) for the list of WSDL definitions and authentication requirements for the SOAP call you are making http://www.paymentsgateway.com/developerDocumentation/Integration/webservices.aspx
For example, to make a SOAP call to create or client and payment method token, here are the needed authentication credentials, which can be found on the following link:
https://sandbox.paymentsgateway.net/WS/Client.wsdl
<xsd:complexType name="Authentication">
<xsd:sequence>
<xsd:element name="APILoginID" type="xsd:string"/>
<xsd:element name="TSHash" type="xsd:string"/>
<xsd:element name="UTCTime" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
<xsd:element name="Authentication" nillable="true" type="tns:Authentication"/>
Otherwise, if you are attempting a call to create a transaction using the AGI transaction Web Services, all you need is the merchant ID and processing password as shown in the WSDL definition header below:
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<ExecuteSocketQuery xmlns="http://paymentsgateway.achdirect.com">
<pg_merchant_id>string</pg_merchant_id>
<pg_password>string</pg_password>
<pg_transaction_type>string</pg_transaction_type>
........................................
Source: https://ws.paymentsgateway.net/pg/paymentsgateway.asmx