Magento – Magento SOAP V2 API Unknown error

this is the first time I use Magento, and I'm trying to make an API, but Im getting some errors.
When I try to call a custom SOAP api method, I'm getting this error:

Uncaught SoapFault exception: [Receiver] Unknown error.

Any ideas?

This is my folder structure:

 --->Company

   --->MobileApi

      --->Model
          --->Mobile
              ---->Api
                    ---->V2.php
                   Api.php

      --->etc
              ---->api.xml
              ---->config.xml
              ---->wsdl.xml
              ---->wsi.xml

api.xml

<?xml version="1.0"?>
<config>
  <api>
    <resources>
      <mobileapi_mobile translate="title" module="mobileapi">
        <model>mobileapi/mobile_api</model>
        <title>Mobile Api</title>
        <!--<acl>mobileapi/mobile</acl>-->
        <methods>
          <forgotaccess translate="title" module="mobileapi">
            <title>Forget the access to the Platform</title>
             <method>forgotaccess</method>
          </forgotaccess>
        </methods>
      </mobileapi_mobile>
    </resources>
    <resources_alias>
      <mobile>mobileapi_mobile_mobile</mobile>
    </resources_alias>
    <v2>
      <resources_function_prefix>
         <mobileapiMobile>mobileapiMobile</mobileapiMobile>
      </resources_function_prefix>
    </v2>
  </api>

config.xml

 <?xml version="1.0"?>
<config>
  <modules>
    <Company_MobileApi>
      <version>1.0</version>
    </Company_MobileApi>
  </modules>
  <global>
    <models>
      <company_mobileapi>
        <class>Company_MobileApi_Model</class>
      </company_mobileapi>
    </models>
    <helpers>
      <company_mobileapi>
        <class>Company_MobileApi_Helper</class>
      </company_mobileapi>
    </helpers>
  </global>
</config>

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/" />

      <element name="mobileapiMobileForgotaccessRequestParam">
        <complexType>
          <sequence>
            <element minOccurs="1" maxOccurs="1" name="sessionId" type="xsd:string" />
            <element minOccurs="1" maxOccurs="1" name="username" type="xsd:string" />
          </sequence>
        </complexType>
      </element>
      <element name="mobileapiMobileForgotaccessResponseParam">
        <complexType>
          <sequence>
            <element minOccurs="1" maxOccurs="1" name="response" type="xsd:string" />

          </sequence>
        </complexType>
      </element>
    </schema>
  </types>

  <message name="mobileapiMobileForgotaccessRequest">
    <part name="parameters" element="typens:mobileapiMobileForgotaccessRequestParam" />
  </message>
  <message name="mobileapiMobileForgotaccessResponse">
    <wsdl:part name="parameters" element="typens:mobileapiMobileForgotaccessResponseParam" />
  </message>
  <portType name="{{var wsdl.handler}}PortType">
    <operation name="mobileapiMobileForgotaccess">
      <documentation>Forgot the access</documentation>
      <input message="typens:mobileapiMobileForgotaccessRequest" />
      <output message="typens:mobileapiMobileForgotaccessResponse" />
    </operation>
  </portType>
  <binding name="{{var wsdl.handler}}Binding" type="typens:{{var wsdl.handler}}PortType">
    <soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http" />
    <operation name="mobileapiMobileForgotaccess">
      <soap:operation soapAction="urn:{{var wsdl.handler}}Action" />
      <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.name}}Service">
    <port name="{{var wsdl.handler}}Port" binding="typens:{{var wsdl.handler}}Binding">
      <soap:address location="{{var wsdl.url}}" />
    </port>
  </service>
</definitions>

wsi.xml

<?xml version="1.0" encoding="UTF-8"?>
<wsdl: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/"
             name="{{var wsdl.name}}"
             targetNamespace="urn:{{var wsdl.name}}">
    <wsdl:types>
        <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:{{var wsdl.name}}">

            <xsd:element name="mobileapiMobileForgotaccessRequestParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="sessionId" type="xsd:string" />
                        <xsd:element minOccurs="1" maxOccurs="1" name="username" type="xsd:string" />
                    </xsd:sequence>
                </xsd:complexType>
            </xsd:element>
            <xsd:element name="mobileapiMobileForgotaccessResponseParam">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element minOccurs="1" maxOccurs="1" name="response" type="xsd:string" />

                    </xsd:sequence>
                </xsd:complexType>
            </xsd:element>
          <!--<xsd:complexType name="mobileapiMobileForgotaccessRequestParam">-->

        </xsd:schema>
    </wsdl:types>

    <wsdl:message name="mobileapiMobileForgotaccessRequest">
        <wsdl:part name="parameters" element="typens:mobileapiMobileForgotaccessRequestParam" />
    </wsdl:message>
    <wsdl:message name="mobileapiMobileForgotaccessResponse">
        <wsdl:part name="parameters" element="typens:mobileapiMobileForgotaccessResponseParam" />
    </wsdl:message>

    <wsdl:portType name="{{var wsdl.handler}}PortType">

         <wsdl:operation name="mobileapiMobileForgotaccess">
            <wsdl:documentation>Forgot the access</wsdl:documentation>
            <wsdl:input message="typens:mobileapiMobileForgotaccessRequest" />
            <wsdl:output message="typens:mobileapiMobileForgotaccessResponse" />
        </wsdl:operation>
    </wsdl:portType>
    <wsdl:binding name="{{var wsdl.handler}}Binding" type="typens:{{var wsdl.handler}}PortType">
      <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" />

    <wsdl:operation name="mobileapiMobileForgotaccess">
      <soap:operation soapAction="urn:{{var wsdl.handler}}Action" />
      <wsdl:input>
        <soap:body  use="literal" />
      </wsdl:input>
      <wsdl:output>
        <soap:body  use="literal" />
      </wsdl:output>
    </wsdl:operation>
  </wsdl:binding>
   <wsdl:service name="{{var wsdl.name}}Service">
    <wsdl:port name="{{var wsdl.handler}}Port" binding="typens:{{var wsdl.handler}}Binding">
      <soap:address location="{{var wsdl.url}}" />
    </wsdl:port>
  </wsdl:service>
</wsdl:definitions>

V2.php

class Company_MobileApi_Model_Mobile_Api_V2 extends Company_MobileApi_Model_Mobile_Api
{

public function forgotaccess($sessionId,$username){

    echo 'hey this is the username'.$username.'and the sessionId:'.$sessionId;

}

}

Api.xml

class Company_MobileApi_Model_Mobile_Api extends Mage_Api_Model_Resource_Abstract
{

public function forgotaccess($sessionId, $username)
{

    echo 'hey this is the username'.$username.'and the sessionId:'.$sessionId;

}
}

This is how I'm calling the api method

error_reporting(E_ALL);
ini_set('display_errors', TRUE);
$api_url = "http://localhost/index.php/api/v2_soap/?wsdl=1"; 

$username = '******';
$password = '******';

$client = new SoapClient($api_url,array('cache_wsdl' => WSDL_CACHE_NONE));

//var_dump($client->__getFunctions());
//retreive session id from login
$session = $client->login(array("username"=>$username,"apiKey"=>$password));
$session= $session->result;


$result = $client->mobileapiMobileForgotaccess(array("sessionId"=>$session,"username"=>"test@test.com")); 

btw, I have the WS-I enable and I'm seeing the mobileapiMobileForgotaccess method in the function list.