Mryntu

app/code/local/Envanto/customapimodule/etc/api.xml

<?xml version="1.0"?>
<config>
 <api>
 <resources>
 <customapimodule_product translate="title" module="customapimodule">
 <model>customapimodule/product_api</model>
 <title>Demo Custommoduleapi API</title>
 <acl>customapimodule/product</acl>
 <methods>
 <list translate="title" module="customapimodule">
 <title>List of products</title>
 <method>items</method>
 </list>
 <info translate="title" module="portfolio"><!-- project details -->
 <title>Retrieve product info</title>
 <acl>customapimodule/product/info</acl>
 </info>
 </methods>
 </customapimodule_product>
 </resources>
 <resources_alias>
 <product>customapimodule_product</product>
 </resources_alias>
 <v2>
 <resources_function_prefix>
 <product>customapimoduleProduct</product>
 </resources_function_prefix>
 </v2>
 <acl>
 <resources>
 <customapimodule translate="title" module="customapimodule">
 <title>Products</title>
 <sort_order>5</sort_order>
 <product translate="title" module="customapimodule">
 <title>Product data</title>
 <info translate="title" module="customapimodule">
 <title>Info</title>
 </info>
 </product>
 </customapimodule>
 </resources>
 </acl>
 </api>
</config>

app/code/local/Envanto/customapimodule/etc/wsdl.xml

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns:typens="urn:var wsdl.name" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
 xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns="http://schemas.xmlsoap.org/wsdl/"
 name="var wsdl.name" targetNamespace="urn:var wsdl.name">
 <types>
 <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:Magento">
 <import namespace="http://schemas.xmlsoap.org/soap/encoding/" schemaLocation="http://schemas.xmlsoap.org/soap/encoding/" />
 <complexType name="fieldInfo">
 <sequence>
 <element name="entity_id" type="xsd:string"/>
 <element name="name" type="xsd:string"/>
 </sequence>
 </complexType>
 <complexType name="fieldInfoArray">
 <complexContent>
 <restriction base="soapenc:Array">
 <attribute ref="soapenc:arrayType" wsdl:arrayType="typens:fieldInfo[]" />
 </restriction>
 </complexContent>
 </complexType>
 <complexType name="customapimoduleProductListEntity"><!-- define type for project list -->
 <all>
 <element name="entity_id" type="xsd:string" minOccurs="1" />
 <element name="name" type="xsd:string" minOccurs="1" />
 <element name="description" type="xsd:string" minOccurs="0" />
 <element name="status" type="xsd:string" minOccurs="0" />
 <element name="created_at" type="xsd:string" minOccurs="1" />
 <element name="updated_at" type="xsd:string" minOccurs="1" />
 </all>
 </complexType>
 <complexType name="customapimoduleProductListEntityArray"><!-- define type array of projects -->
 <complexContent>
 <restriction base="soapenc:Array">
 <attribute ref="soapenc:arrayType" wsdl:arrayType="typens:customapimoduleProductListEntity[]" />
 </restriction>
 </complexContent>
 </complexType>
 <complexType name="customapimoduleProductInfoEntity"><!-- define type for retrieve info -->
 <all>
 <element name="entity_id" type="xsd:string" minOccurs="1" />
 <element name="name" type="xsd:string" minOccurs="1" />
 <element name="description" type="xsd:string" minOccurs="0" />
 <element name="status" type="xsd:string" minOccurs="0" />
 <element name="created_at" type="xsd:string" minOccurs="1" />
 <element name="updated_at" type="xsd:string" minOccurs="1" />
 </all>
 </complexType>

 </schema>
 </types>
 <message name="customapimoduleProductListRequest">
 <part name="sessionId" type="xsd:string" />
 </message>
 <message name="customapimoduleProductListResponse">
 <part name="products" type="typens:fieldInfoArray" />
 </message>
 <message name="customapimoduleProductInfoRequest">
 <part name="sessionId" type="xsd:string" />
 <part name="productSku" type="xsd:string" />
 </message>
 <message name="customapimoduleProductInfoResponse">

 <part name="result" type="typens:fieldInfoArray" />
 </message>

 <portType name="var wsdl.handlerPortType">
 <operation name="customapimoduleProductList">
 <documentation>List of products</documentation>
 <input message="typens:customapimoduleProductListRequest" />
 <output message="typens:customapimoduleProductListResponse" />
 </operation>
 <operation name="customapimoduleProductInfo">
 <documentation>Retrieve product info</documentation>
 <input message="typens:customapimoduleProductInfoRequest" />
 <output message="typens:customapimoduleProductInfoResponse" />
 </operation>
 </portType>
 <binding name="var wsdl.handlerBinding" type="typens:var wsdl.handlerPortType">
 <soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http" />
 <operation name="customapimoduleProductList">
 <soap:operation soapAction="urn:var wsdl.handlerAction" />
 <input>
 <soap:body namespace="urn:var wsdl.name" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
 </input>
 <output>
 <soap:body namespace="urn:var wsdl.name" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
 </output>
 </operation>
 <operation name="customapimoduleProductInfo">
 <soap:operation soapAction="urn:var wsdl.handlerAction" />
 <input>
 <soap:body namespace="urn:var wsdl.name" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
 </input>
 <output>
 <soap:body namespace="urn:var wsdl.name" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
 </output>
 </operation>
 </binding>
 <service name="var wsdl.nameService">
 <port name="var wsdl.handlerPort" binding="typens:var wsdl.handlerBinding">
 <soap:address location="var wsdl.url" />
 </port>
 </service>
</definitions>

My problem is that now custom function called but in built function like "catalogProductInfo" not called give error Invalid API PATH.