How to use mutiple values in input parameters in soap call - soap

Question

I have a current requirement where I need to make a soap call to retrieve the data for further business intelligence. I have no experience in SOAP.
The service call is called getSiteInfo.
getSiteInfo has following 4 parameters- userName, password, custNbr, siteId.
Now I can make calls like this and it generates an xml response
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:bil="http://billing.xyz.cc/">
<soapenv:Header/>
<soapenv:Body>
<bil:getSiteInfo>
<!--userName:-->
<arg0>username</arg0>
<!--password:-->
<arg1>pswd</arg1>
<!--custNbr:-->
<arg2>288</arg2>
<!--siteId:-->
<arg3>0862578</arg3>
</bil:getSiteInfo>
</soapenv:Body>
</soapenv:Envelope>
I was wondering is it possible to include multiple siteId in the same call instead of doing it repeatedly for almost 1000+ siteIds.
I tried the following two to see if they work and none of them did. It only returned the response for the last item; 108952 in this case.
Method1
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:bil="http://billing.xyz.cc/">
<soapenv:Header/>
<soapenv:Body>
<bil:getSiteInfo>
<!--userName:-->
<arg0>username</arg0>
<!--password:-->
<arg1>pswd</arg1>
<!--customerNumber:-->
<arg2>288</arg2>
<!--siteNumber:-->
<arg3>0862578</arg3>
<arg3>108952</arg3>
</bil:getSiteInfo>
</soapenv:Body>
</soapenv:Envelope>
Method2
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:bil="http://billing.xyz.cc/">
<soapenv:Header/>
<soapenv:Body>
<bil:getSiteInfo>
<!--userName:-->
<arg0>username</arg0>
<!--password:-->
<arg1>pswd</arg1>
<!--customerNumber:-->
<arg2>288</arg2>
<!--siteNumber:-->
<arg3>108952</arg3>
</bil:getSiteInfo>
<bil:getSiteInfo>
<!--userName:-->
<arg0>username</arg0>
<!--password:-->
<arg1>pswd</arg1>
<!--customerNumber:-->
<arg2>288</arg2>
<!--siteNumber:-->
<arg3>0862578</arg3>
</bil:getSiteInfo>
</soapenv:Body>
</soapenv:Envelope>
Thank you very much in advance.