Web service CustCustomerService Query criteria schema

Good evening,

We're currently using the CustCustomerService and would like to pass multiple criteria to the web service to return all customers for a particular sales group and partyCountry.  We are effectively sending:-

'QueryCriteria' => array(

               'CriteriaElement' => array(

                   array(

                       'DataSourceName' => 'CustTable',

                       'FieldName'      => 'PartyCountry',

                       'Operator'       => 'Equal',

                       'Value1'         => $country

                   ),

                   array(

                       'DataSourceName' => 'CustTable',

                       'FieldName'      => 'SalesGroup',

                       'Operator'       => 'Equal',

                       'Value1'         => $salesGroup

                   )

               )

Currently the schema appears to only accept a single element so the results are not what we expect.  Are we passing this incorrectly or is there a way to change the query schema from:-

<xsd:complexType name="QueryCriteria">

    <xsd:sequence minOccurs="1" maxOccurs="unbounded">

        <xsd:element name="CriteriaElement" type="tns:CriteriaElement"/>

    </xsd:sequence>

</xsd:complexType>

to:

<xsd:complexType name="QueryCriteria">

    <xsd:sequence>

        <xsd:element minOccurs="1" maxOccurs="unbounded" name="CriteriaElement" type="tns:CriteriaElement"/>

    </xsd:sequence>

</xsd:complexType>

Many thanks

Paulina