Here it is
<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="
http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="
https://adwords.google.com/api/adwords/cm/v201306" xmlns:ns2="
https://adwords.google.com/api/adwords/mcm/v201306">
<SOAP-ENV:Header>
<ns2:RequestHeader>
<ns1:clientCustomerId>***-***-****</ns1:clientCustomerId>
<ns1:developerToken>****************</ns1:developerToken>
<ns1:userAgent>Adwords API Testing (AwApi-PHP/5.0.0, Common-PHP/5.0.0, PHP/5.4.7)</ns1:userAgent>
</ns2:RequestHeader>
</SOAP-ENV:Header>
<SOAP-ENV:Body>
<ns2:mutateLink>
<ns2:operations>
<ns1:operator>ADD</ns1:operator>
<ns2:operand>
<ns2:managerCustomerId>1**-**-****</ns2:managerCustomerId>
<ns2:clientCustomerId>1**-**-****</ns2:clientCustomerId>
<ns2:linkStatus>PENDING</ns2:linkStatus>
</ns2:operand>
</ns2:operations>
</ns2:mutateLink>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
HTTP/1.1 500 Internal Server Error
Content-Type: text/xml; charset=UTF-8
Content-Encoding: gzip
Date: Mon, 29 Jul 2013 04:45:58 GMT
Expires: Mon, 29 Jul 2013 04:45:58 GMT
Cache-Control: private, max-age=0
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
Content-Length: 575
Server: GSE
<?xml version="1.0"?>
<soap:Envelope xmlns:soap="
http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header>
<ResponseHeader xmlns:ns2="
https://adwords.google.com/api/adwords/cm/v201306" xmlns="
https://adwords.google.com/api/adwords/mcm/v201306">
<ns2:requestId>0004e29f2b23fd780a835f0100006abd</ns2:requestId>
<ns2:serviceName>ManagedCustomerService</ns2:serviceName>
<ns2:methodName>mutateLink</ns2:methodName>
<ns2:operations>1</ns2:operations>
<ns2:responseTime>229</ns2:responseTime>
</ResponseHeader>
</soap:Header>
<soap:Body>
<soap:Fault>
<faultcode>soap:Server</faultcode>
<faultstring>[InternalApiError.UNEXPECTED_INTERNAL_API_ERROR @ com.google.ads.api.services.common.error.InternalApiError.<init>(InternalApiErro]</faultstring>
<detail>
<ApiExceptionFault xmlns="
https://adwords.google.com/api/adwords/mcm/v201306" xmlns:ns2="
https://adwords.google.com/api/adwords/cm/v201306">
<ns2:message>[InternalApiError.UNEXPECTED_INTERNAL_API_ERROR @ com.google.ads.api.services.common.error.InternalApiError.<init>(InternalApiErro]</ns2:message>
<ns2:ApplicationException.Type>ApiException</ns2:ApplicationException.Type>
<ns2:errors xmlns:xsi="
http://www.w3.org/2001/XMLSchema-instance" xsi:type="ns2:InternalApiError">
<ns2:fieldPath/>
<ns2:trigger/>
<ns2:errorString>InternalApiError.UNEXPECTED_INTERNAL_API_ERROR</ns2:errorString>
<ns2:ApiError.Type>InternalApiError</ns2:ApiError.Type>
<ns2:reason>UNEXPECTED_INTERNAL_API_ERROR</ns2:reason>
</ns2:errors>
</ApiExceptionFault>
</detail>
</soap:Fault>
</soap:Body>
</soap:Envelope>